Insulin: Uses, Dosage & Side Effects
A life-saving hormone replacement used to manage blood sugar in people with diabetes mellitus, available as long-acting, rapid-acting, and mixed formulations
Insulin is a vital hormone that regulates blood sugar (glucose) levels. People with type 1 diabetes produce no insulin at all, while those with type 2 diabetes may not produce enough or may not respond properly to the insulin their body makes. Insulin therapy replaces or supplements the body's natural insulin to keep blood sugar within a safe range. Insulin glargine is one of the most commonly prescribed long-acting insulin analogues, providing a steady baseline of insulin for up to 24 hours with a single daily injection. Insulin is listed on the WHO Model List of Essential Medicines and is used by hundreds of millions of people worldwide.
Quick Facts: Insulin
Key Takeaways
- Insulin is essential for people with type 1 diabetes and many with type 2 diabetes to control blood sugar and prevent life-threatening complications.
- Insulin glargine (Lantus, Toujeo) is a long-acting insulin given once daily, providing steady blood sugar control for up to 24 hours without a pronounced peak.
- Hypoglycemia (low blood sugar) is the most common side effect — always carry a fast-acting sugar source and monitor blood glucose regularly.
- Never inject insulin into a vein, never mix insulin glargine with other insulins, and always rotate injection sites to prevent skin changes.
- Store unopened insulin in the refrigerator (2–8°C); once opened, it can be kept at room temperature for up to 4 weeks.
What Is Insulin and What Is It Used For?
Insulin is one of the most important hormones in the human body. It is produced by the beta cells of the pancreas and acts as a key that unlocks cells, allowing glucose (sugar) from the food you eat to enter and be used as energy. Without adequate insulin, glucose accumulates in the bloodstream, leading to dangerously high blood sugar levels that can cause both short-term and long-term health complications.
Diabetes mellitus is a chronic metabolic disorder in which the body's ability to produce or respond to insulin is impaired. In type 1 diabetes, an autoimmune process destroys the insulin-producing beta cells, resulting in absolute insulin deficiency. People with type 1 diabetes must take insulin injections from the time of diagnosis for the rest of their lives. In type 2 diabetes, the body initially becomes resistant to insulin's effects, and over time, the pancreas may also fail to produce sufficient amounts. Many people with advanced type 2 diabetes eventually require insulin therapy, particularly when oral medications alone no longer provide adequate blood sugar control.
Insulin glargine is a modified form of human insulin classified as a long-acting insulin analogue. After subcutaneous injection, it forms microprecipitates that dissolve slowly, providing a steady and prolonged release of insulin over approximately 24 hours. Unlike older insulin preparations, insulin glargine has no pronounced peak in action, which reduces the risk of hypoglycemia, particularly overnight. It is approved for use in adults, adolescents, and children aged 2 years and older with diabetes mellitus.
Insulin glargine is typically used as basal insulin — the background level of insulin needed to control blood sugar between meals and during sleep. In type 1 diabetes, it is always combined with a rapid-acting mealtime insulin (basal-bolus regimen). In type 2 diabetes, it may be used alone or in combination with oral antidiabetic medications, GLP-1 receptor agonists, or mealtime insulin, depending on the individual's needs and treatment goals.
According to the International Diabetes Federation, approximately 537 million adults worldwide live with diabetes, and this number is expected to rise to 783 million by 2045. Insulin remains the cornerstone of diabetes management and is listed on the WHO Model List of Essential Medicines, underscoring its critical importance in global health.
What Should You Know Before Taking Insulin?
Contraindications
You should not use insulin glargine if you are allergic (hypersensitive) to insulin glargine or any of the other ingredients in the formulation, including zinc chloride, metacresol, glycerol, sodium hydroxide, hydrochloric acid, polysorbate 20, or water for injections. Signs of an allergic reaction may include skin rash, itching, swelling of the face or throat, difficulty breathing, rapid heartbeat, and sweating. If you experience a severe allergic reaction, seek emergency medical care immediately.
Warnings and Precautions
Talk to your doctor, pharmacist, or diabetes nurse before using insulin glargine. Careful attention to dosing instructions, blood glucose monitoring, diet, and physical activity is essential for safe and effective insulin therapy. Several important considerations apply:
- Hypoglycemia (low blood sugar): This is the most common and potentially serious adverse effect of insulin therapy. Learn to recognize the symptoms (sweating, trembling, rapid heartbeat, confusion) and always carry a source of fast-acting sugar. Your risk of hypoglycemia is increased if you skip meals, exercise more than usual, drink alcohol, or change your insulin dose.
- Hyperglycemia (high blood sugar): Illness, infection, stress, surgery, or missed insulin doses can cause blood sugar levels to rise dangerously. If you are unwell, monitor your blood sugar more frequently and contact your healthcare provider for guidance on dose adjustments.
- Skin changes at injection sites: Repeatedly injecting in the same spot can cause the skin to shrink (lipoatrophy) or thicken (lipohypertrophy). Lumps under the skin can also be caused by a build-up of a protein called amyloid (cutaneous amyloidosis). These changes can affect how well insulin is absorbed. Always rotate your injection sites and consult your doctor before switching away from an area with lumps.
- Insulin switching: Insulin glargine 100 units/ml (Lantus) and insulin glargine 300 units/ml (Toujeo) are not interchangeable without medical supervision. Switching between insulin types requires a new prescription, dose adjustment, and increased blood sugar monitoring.
- Insulin antibodies: Insulin therapy can, in very rare cases, cause the body to produce antibodies against insulin. This usually does not require a change in treatment, but in extremely rare cases, a dose adjustment may be necessary.
Before travelling, consult your doctor about insulin availability in your destination country, appropriate storage during transit, adjustment of injection times across time zones, and carrying medical identification. Always carry your insulin and supplies in your hand luggage when flying, as checked luggage may freeze in the aircraft hold.
Pregnancy and Breastfeeding
If you are pregnant, planning to become pregnant, or breastfeeding, talk to your doctor before using any medication. Insulin is the preferred treatment for diabetes during pregnancy because it does not cross the placenta in significant amounts and is considered safe for the developing baby. Good blood sugar control is particularly important during pregnancy to prevent complications for both mother and child, including pre-eclampsia, macrosomia (large baby), birth defects, and neonatal hypoglycemia.
Insulin requirements typically change throughout pregnancy. They may decrease during the first trimester and then increase significantly during the second and third trimesters due to increasing insulin resistance. After delivery, insulin requirements usually drop rapidly and may need to be adjusted. If you are breastfeeding, your insulin dose and diet may also need to be adjusted, as lactation can lower blood sugar levels.
Use in Children
Insulin glargine (Lantus) is approved for use in children aged 2 years and older. There is no clinical experience with insulin glargine in children under 2 years of age. Dosing for children should be carefully individualized by a paediatric endocrinologist, and parents and caregivers must be thoroughly trained in injection technique, blood sugar monitoring, and hypoglycemia management.
Driving and Operating Machinery
Your ability to concentrate and react may be impaired if you experience hypoglycemia (low blood sugar) or hyperglycemia (high blood sugar), or if you have problems with your vision as a result of these conditions. Keep this in mind in all situations where you could put yourself or others at risk, such as driving a car or operating machinery. Contact your doctor for advice about driving if you have frequent episodes of hypoglycemia or if the warning symptoms of hypoglycemia are weakened or absent.
How Does Insulin Interact with Other Drugs?
Drug interactions with insulin are clinically significant because they can either increase or decrease blood sugar levels, sometimes unpredictably. Understanding these interactions is essential for safe diabetes management. Your doctor may need to adjust your insulin dose when you start, stop, or change the dose of another medication.
Drugs That May Lower Blood Sugar (Increase Hypoglycemia Risk)
The following medications can enhance the blood sugar-lowering effect of insulin. When these drugs are used in combination with insulin, your risk of hypoglycemia increases and closer blood sugar monitoring is recommended:
| Drug/Class | Primary Indication | Interaction Mechanism |
|---|---|---|
| Other antidiabetic drugs (metformin, sulfonylureas, GLP-1 agonists) | Diabetes | Additive blood sugar-lowering effect |
| ACE inhibitors (enalapril, ramipril, lisinopril) | High blood pressure, heart failure | May increase insulin sensitivity |
| Fluoxetine (Prozac) | Depression | Enhances insulin action |
| MAO inhibitors | Depression | May potentiate insulin effect |
| Salicylates (aspirin, high doses) | Pain, inflammation | Reduces hepatic glucose production |
| Fibrates (fenofibrate, gemfibrozil) | High cholesterol/triglycerides | May increase insulin sensitivity |
| Sulfonamide antibiotics | Bacterial infections | May enhance insulin secretion |
| Pentoxifylline | Peripheral vascular disease | May lower blood glucose |
| Disopyramide | Heart rhythm disorders | Direct hypoglycemic effect |
Drugs That May Raise Blood Sugar (Decrease Insulin Effectiveness)
The following medications can counteract the effects of insulin and raise blood sugar levels. An increase in insulin dose may be required when starting these medications:
| Drug/Class | Primary Indication | Interaction Mechanism |
|---|---|---|
| Corticosteroids (prednisolone, dexamethasone) | Inflammation, autoimmune conditions | Increases insulin resistance and hepatic glucose output |
| Thyroid hormones (levothyroxine) | Hypothyroidism | Increases glucose absorption and production |
| Diuretics (thiazides, furosemide) | High blood pressure, fluid retention | Impairs insulin secretion, potassium depletion |
| Oral contraceptives (estrogen/progestogen) | Contraception | Increases insulin resistance |
| Somatropin (growth hormone) | Growth hormone deficiency | Counter-regulatory to insulin |
| Sympathomimetics (salbutamol, terbutaline, epinephrine) | Asthma, allergic reactions | Stimulates glycogenolysis and gluconeogenesis |
| Atypical antipsychotics (olanzapine, clozapine) | Psychiatric disorders | Causes weight gain and insulin resistance |
| Isoniazid | Tuberculosis | Impairs glucose tolerance |
| Protease inhibitors (ritonavir, lopinavir) | HIV infection | Causes insulin resistance |
Drugs with Variable Effects on Blood Sugar
Some medications may either raise or lower blood sugar depending on the circumstances. These include beta-blockers (used for high blood pressure and heart conditions), clonidine (used for high blood pressure), and lithium salts (used for mood disorders). Beta-blockers are particularly important because they can mask the typical warning signs of hypoglycemia (such as rapid heartbeat and trembling), making it harder for you to recognize low blood sugar. If you take beta-blockers, you may need to monitor your blood glucose more frequently.
Pentamidine (used for certain parasitic infections) may cause hypoglycemia that can sometimes be followed by hyperglycemia. Alcohol can both raise and lower blood sugar levels depending on the amount consumed and whether it is taken with food. Alcohol can cause delayed hypoglycemia for up to 24 hours after consumption, and the symptoms of alcohol intoxication may be confused with those of hypoglycemia.
Always tell your doctor or pharmacist about all medications you are taking, including prescription drugs, over-the-counter medicines, and herbal supplements. Never start or stop a medication without discussing the potential impact on your blood sugar control with your healthcare provider.
What Is the Correct Dosage of Insulin?
The dosage of insulin is one of the most individualized aspects of diabetes treatment. There is no fixed dose that works for everyone. Your healthcare provider will determine your starting dose and adjust it over time based on your blood sugar readings, HbA1c levels, diet, physical activity, body weight, other medications, and any concurrent illnesses. The goal is to maintain blood sugar levels as close to normal as possible while minimizing the risk of hypoglycemia.
Adults
Insulin Glargine 100 units/ml (Lantus, Abasaglar)
Administered as one injection per day, at the same time each day. The starting dose is typically 10 units per day or 0.1–0.2 units/kg/day for type 2 diabetes, adjusted upward by 2–4 units every 3–7 days based on fasting blood glucose readings. For type 1 diabetes, basal insulin usually represents approximately 40–50% of the total daily insulin dose, with the remainder given as rapid-acting mealtime insulin.
Insulin Glargine 300 units/ml (Toujeo)
Administered as one injection per day. Provides a more gradual and extended absorption profile compared to the 100 units/ml formulation. When switching from Lantus 100 units/ml to Toujeo 300 units/ml, a dose increase of approximately 10–18% may be needed to maintain equivalent blood sugar control. This switch should only be done under medical supervision.
Children (aged 2 years and older)
Paediatric Dosing
Insulin glargine 100 units/ml can be used in children aged 2 years and older. The dose is individually determined by the child's paediatric endocrinologist based on age, weight, blood sugar levels, physical activity, and growth. Children's insulin requirements may change during puberty and periods of rapid growth. Parents and caregivers must be thoroughly trained in injection technique, blood sugar monitoring, and recognizing and treating hypoglycemia.
Elderly Patients
Older Adults (65+ years)
In elderly patients, progressive deterioration of kidney function may lead to a steady decrease in insulin requirements. Blood sugar targets may be less strict in older adults to reduce the risk of hypoglycemia, which can be particularly dangerous in this population due to increased fall risk and cardiovascular vulnerability. Careful monitoring and gradual dose adjustments are recommended.
Injection Technique
Insulin glargine is injected subcutaneously (under the skin) only. It must never be injected into a vein, as this would dramatically alter its action and could cause severe hypoglycemia. The recommended injection sites include:
- Abdomen: Most consistent absorption; avoid a 5 cm area around the navel
- Thighs: Outer upper area; slightly slower absorption
- Upper arms: Outer area; may be difficult to self-inject
Rotate injection sites within the same region each time to reduce the risk of lipodystrophy (skin thickening or thinning at the injection site). Before each injection, check the insulin to ensure it is clear, colorless, and free of particles. Do not shake the insulin. Do not mix or dilute insulin glargine with any other insulin or solution, as this may change its action profile.
Always check the insulin label before each injection to avoid mix-ups between different insulin types. Accidentally injecting rapid-acting insulin instead of long-acting insulin (or vice versa) can cause dangerous blood sugar fluctuations. If you use multiple types of insulin, keep them clearly labeled and stored separately.
Missed Dose
If you forget to take your insulin glargine dose, your blood sugar may rise too high (hyperglycemia). Check your blood sugar frequently and take your dose as soon as you remember, unless it is almost time for your next scheduled dose. Do not take a double dose to make up for a forgotten injection. If you are unsure what to do, contact your doctor or diabetes nurse for guidance. For information on managing hyperglycemia, see the hyperglycemia section below.
Overdose
If you inject too much insulin, your blood sugar may drop to dangerously low levels (hypoglycemia). Mild hypoglycemia can usually be managed by eating 15–20 grams of fast-acting carbohydrates (such as glucose tablets, fruit juice, or regular soft drink). Check your blood sugar 15 minutes later and repeat if necessary. Severe hypoglycemia — where you are unable to treat yourself or become unconscious — is a medical emergency. Someone nearby should administer a glucagon injection and call emergency services immediately. Because insulin glargine is long-acting, recovery from hypoglycemia may be prolonged, requiring extended monitoring and repeated carbohydrate intake.
Stopping insulin therapy abruptly, especially in type 1 diabetes, can lead to diabetic ketoacidosis (DKA) — a life-threatening condition where the body breaks down fat instead of sugar for energy, causing a dangerous build-up of acids (ketones) in the blood. Symptoms include excessive thirst, frequent urination, nausea, vomiting, abdominal pain, rapid deep breathing, and drowsiness. DKA requires immediate hospital treatment. Never stop or reduce your insulin without your doctor's guidance.
What Are the Side Effects of Insulin?
Like all medicines, insulin can cause side effects, although not everyone experiences them. Understanding the potential side effects and their frequency helps you recognize them early and take appropriate action. The side effects of insulin are classified by how commonly they occur:
Very Common
May affect more than 1 in 10 people
- Hypoglycemia (low blood sugar) — The most frequent and potentially most serious side effect. Symptoms include sweating, clammy skin, trembling, rapid heartbeat, palpitations, anxiety, hunger, dizziness, tingling around the mouth, headache, confusion, irritability, difficulty concentrating, drowsiness, and in severe cases, seizures or loss of consciousness. Severe hypoglycemia can cause brain damage and can be life-threatening.
Common
May affect up to 1 in 10 people
- Injection site reactions — Redness, unusually intense pain during injection, itching, hives (urticaria), swelling, or inflammation at the injection site. Most mild reactions resolve within a few days to a few weeks.
- Lipohypertrophy — Thickening of the skin at injection sites due to repeated injections in the same area. May affect insulin absorption.
Uncommon
May affect up to 1 in 100 people
- Lipoatrophy — Shrinking or thinning of the fat tissue at injection sites. Prevented by rotating injection sites consistently.
Rare
May affect up to 1 in 1,000 people
- Severe allergic reactions (anaphylaxis) — Widespread skin reactions (rash and itching over the entire body), severe swelling of the skin or mucous membranes (angioedema), shortness of breath, drop in blood pressure with rapid heartbeat and sweating. This is a medical emergency — seek immediate medical help.
- Visual disturbances — A marked change in blood sugar control (improvement or worsening) can temporarily impair vision. If you have proliferative retinopathy (a diabetic eye disease), severe hypoglycemic episodes may cause temporary vision loss.
- Oedema (fluid retention) — Insulin treatment can, in rare cases, cause temporary fluid retention with swelling of the calves and ankles, particularly when initiating therapy or when blood sugar control is rapidly improved.
Very Rare
May affect up to 1 in 10,000 people
- Dysgeusia — Changes in taste perception
- Myalgia — Muscle pain
Cutaneous Amyloidosis (Frequency Not Known)
Lumps under the skin may also be caused by a build-up of a protein called amyloid (cutaneous amyloidosis). The frequency of this side effect is not precisely known. Insulin may not work as effectively if injected into an area with lumps. Change your injection site with each injection to help prevent these skin changes.
Side Effects in Children and Adolescents
In general, the side effects in children and adolescents aged 18 years or younger are similar to those seen in adults. However, complaints of injection site reactions (pain at the injection site, injection site reactions) and skin reactions (rash, hives) are reported relatively more frequently in children and adolescents compared to adults. There is no clinical experience with insulin glargine in children under the age of 2 years.
Some patients with long-standing type 2 diabetes and heart disease or previous stroke, who were treated with both pioglitazone (an oral diabetes medicine) and insulin, developed heart failure. Inform your doctor immediately if you experience signs of heart failure, such as increasing shortness of breath, rapid weight gain, or localized swelling (oedema).
Recognizing and Managing Hypoglycemia
Because hypoglycemia is the most important side effect of insulin, understanding how to recognize and manage it is crucial for every person using insulin:
Step 1: Do not inject more insulin. Immediately consume 15–20 grams of fast-acting sugar: glucose tablets, sugar cubes, fruit juice, or a sugar-sweetened drink. Artificial sweeteners do NOT help.
Step 2: Follow up with a slower-acting carbohydrate (bread, crackers, or a meal) to prevent blood sugar from dropping again.
Step 3: Check your blood sugar after 15 minutes. If it is still low, repeat step 1.
Step 4: If hypoglycemia recurs or you cannot control it, contact your doctor immediately.
If unconscious: Someone nearby must administer a glucagon injection and call emergency services. Do NOT attempt to give food or drink to an unconscious person. Test blood sugar immediately after glucose administration.
Recognizing and Managing Hyperglycemia
Hyperglycemia (high blood sugar) can occur if you have not injected enough insulin, if your insulin has become less effective (e.g., due to improper storage), if you exercise less than usual, are under stress, have an infection or fever, or are taking certain medications. Warning symptoms include excessive thirst, frequent urination, fatigue, dry skin, facial flushing, decreased appetite, low blood pressure, rapid heartbeat, and the presence of glucose and ketone bodies in the urine. Nausea, vomiting, abdominal pain, rapid deep breathing, and drowsiness may indicate a serious condition (ketoacidosis) resulting from insulin deficiency. Test your blood sugar and urine for ketones immediately if these symptoms occur and seek medical care urgently.
How Should You Store Insulin?
Proper storage of insulin is critical for maintaining its effectiveness. Insulin that has been stored incorrectly may lose its potency without any visible changes, leading to unexpectedly poor blood sugar control. Follow these guidelines to ensure your insulin remains safe and effective:
Unopened (Not Yet in Use)
- Store in a refrigerator at 2–8°C
- Do not freeze — frozen insulin is permanently damaged and must be discarded
- Do not store in direct contact with the freezer compartment or ice packs
- Keep in the outer carton to protect from light
- Check the expiry date before use — the expiry date refers to the last day of the stated month
Opened (Currently in Use)
- 5 ml vials: Can be stored for up to 4 weeks at a maximum of 25°C, in the outer carton, protected from direct heat and light
- 10 ml vials: Can be stored for up to 4 weeks at a maximum of 30°C, in the outer carton, protected from direct heat and light
- Pre-filled pens and cartridges: Can be stored for up to 4 weeks at room temperature (up to 25–30°C depending on the product). Do not refrigerate pens that are in use, as cold insulin can be more painful to inject
- Write the date of first use on the label to keep track
- Discard after 4 weeks of opening, even if insulin remains in the pen or vial
Inspect the insulin before use. Insulin glargine should be a clear, colorless, water-like solution with no visible particles. Do not use the insulin if it appears cloudy, discolored, or contains solid particles. If you notice unexpectedly poor blood sugar control, your insulin may have lost effectiveness due to improper storage — replace it with a new pen or vial.
Keep insulin and all medicines out of the sight and reach of children. Do not dispose of insulin via household waste or sewage. Return unused or expired insulin to your pharmacy for safe disposal to protect the environment.
What Does Insulin Contain?
Active Ingredient
The active substance is insulin glargine. Each millilitre of solution contains 100 units of insulin glargine, which corresponds to 3.64 mg of the active compound. Insulin glargine is produced by recombinant DNA technology in Escherichia coli bacteria and is structurally modified from human insulin to provide a prolonged duration of action. Two amino acid changes (asparagine to glycine at position A21, and addition of two arginine residues at the B-chain C-terminus) shift the isoelectric point, causing the molecule to precipitate at physiological pH after subcutaneous injection, resulting in slow and steady absorption.
The concentrated formulation (Toujeo, 300 units/ml) contains three times the concentration of insulin glargine per millilitre, which results in a smaller injection volume and a more prolonged absorption profile, providing an even flatter and more extended blood sugar-lowering effect compared to the 100 units/ml formulation.
Inactive Ingredients (Excipients)
| Ingredient | Purpose |
|---|---|
| Zinc chloride | Stabilizes insulin hexamers and prolongs action |
| Metacresol | Preservative (antimicrobial agent) |
| Glycerol | Tonicity agent (makes solution isotonic) |
| Sodium hydroxide | pH adjustment |
| Hydrochloric acid | pH adjustment |
| Polysorbate 20 (10 ml vial only) | Surfactant (prevents aggregation) |
| Water for injections | Solvent |
This medicine contains less than 1 mmol sodium (23 mg) per dose, meaning it is essentially sodium-free. This is relevant for people on a controlled sodium diet.
Available Forms and Pack Sizes
Insulin glargine 100 units/ml is available as a clear, colorless, water-like solution in:
- Vials: 5 ml (500 units) or 10 ml (1,000 units)
- Cartridges: 3 ml (300 units) for use with compatible insulin pens
- Pre-filled pens: 3 ml (300 units) in disposable pens (e.g., SoloStar, KwikPen)
Insulin glargine 300 units/ml (Toujeo) is available in pre-filled pens containing 1.5 ml (450 units). Not all pack sizes may be available in all countries.
Frequently Asked Questions About Insulin
Long-acting insulins such as insulin glargine (Lantus, Toujeo) and insulin detemir (Levemir) provide a steady baseline level of insulin over 18–24 hours, mimicking the body's natural basal insulin secretion. They are typically injected once or twice daily and have no pronounced peak. Rapid-acting insulins such as insulin lispro (Humalog), insulin aspart (NovoRapid), and insulin glulisine (Apidra) begin working within 10–20 minutes and are taken before meals to cover blood sugar spikes from food. Most people with type 1 diabetes use both types together in what is called a basal-bolus regimen, while some people with type 2 diabetes may only need basal insulin.
If you miss a dose of long-acting insulin like glargine, take it as soon as you remember, unless it is almost time for your next dose. Never take a double dose. Check your blood sugar more frequently after a missed dose and watch for signs of hyperglycemia (excessive thirst, frequent urination, fatigue). If you are more than 12 hours late, check your blood glucose and contact your doctor or diabetes nurse for guidance on adjusting your next dose. If you frequently forget doses, discuss strategies with your healthcare team, such as setting reminders or adjusting your injection schedule to a more convenient time.
Yes, insulin is the preferred treatment for diabetes during pregnancy. It does not cross the placenta in significant amounts and is considered safe for the developing baby. Maintaining good blood sugar control during pregnancy is crucial to prevent complications for both mother and child. Insulin requirements typically change during pregnancy — they may decrease in the first trimester and then increase significantly in the second and third trimesters. After delivery, insulin needs usually drop rapidly. All pregnant women with diabetes should be managed by a multidisciplinary team including an endocrinologist and an obstetrician.
When travelling, keep your insulin in your hand luggage — never in checked baggage, as the cargo hold of an aircraft can reach freezing temperatures. Use an insulated cooling case (available from pharmacies) to protect insulin from heat during warm weather, but ensure the insulin does not come into direct contact with ice or cold packs, as freezing destroys it. Carry a letter from your doctor explaining your need for insulin and syringes/pens, especially for international travel. If crossing time zones, discuss dose timing adjustments with your doctor before your trip. Carry extra supplies (pens, needles, blood glucose monitor, glucose tablets) in case of delays.
Early warning signs of hypoglycemia (low blood sugar) include sweating, trembling, rapid heartbeat, anxiety, hunger, dizziness, pallor, and tingling in the lips or fingers. As blood sugar drops further, you may experience confusion, difficulty concentrating, slurred speech, blurred vision, irritability, drowsiness, and weakness. In severe cases, seizures and loss of consciousness can occur. Some people — particularly those who have had diabetes for a long time, who have had recent hypoglycemic episodes, or who take beta-blockers — may have reduced or absent warning symptoms (hypoglycemia unawareness). If you suspect low blood sugar, always test and treat immediately with fast-acting carbohydrates.
Alcohol can affect blood sugar levels unpredictably when you are using insulin. It may initially raise blood sugar (particularly sweet or mixed drinks) but can cause a delayed and prolonged drop in blood sugar levels, especially if consumed without food. The liver prioritizes metabolizing alcohol over releasing glucose, which impairs the body's ability to correct low blood sugar. If you choose to drink, do so in moderation, always eat food with your drinks, check your blood sugar before bed, and be aware that the symptoms of low blood sugar can be mistaken for intoxication by others. Discuss your alcohol intake with your diabetes team to ensure safe management.
References
- World Health Organization. WHO Model List of Essential Medicines – 23rd List. Geneva: WHO; 2023. Insulin is classified as an essential medicine for diabetes management worldwide.
- European Medicines Agency. Lantus (Insulin Glargine) – Summary of Product Characteristics. EMA; 2025. Official European prescribing information for insulin glargine.
- American Diabetes Association. Standards of Care in Diabetes – 2025. Diabetes Care. 2025;48(Suppl 1). Comprehensive evidence-based clinical practice recommendations for diabetes management.
- Davies MJ, Aroda VR, Collins BS, et al. Management of Hyperglycemia in Type 2 Diabetes, 2022. A Consensus Report by the ADA and EASD. Diabetes Care. 2022;45(11):2753-2786. doi:10.2337/dci22-0034
- International Diabetes Federation. IDF Diabetes Atlas, 10th edition. Brussels: IDF; 2021. Global epidemiological data on diabetes prevalence and projections.
- Riddle MC, Rosenstock J, Gerich J, on behalf of the Insulin Glargine 4002 Study Investigators. The treat-to-target trial: randomized addition of glargine or human NPH insulin to oral therapy of type 2 diabetic patients. Diabetes Care. 2003;26(11):3080-3086. doi:10.2337/diacare.26.11.3080
- Ratner RE, Hirsch IB, Neifing JL, et al. Less hypoglycemia with insulin glargine in intensive insulin therapy for type 1 diabetes. Diabetes Care. 2000;23(5):639-643. doi:10.2337/diacare.23.5.639
- Bolli GB, Owens DR. Insulin glargine. Lancet. 2000;356(9228):443-445. doi:10.1016/S0140-6736(00)02546-0. Review of insulin glargine pharmacology and clinical efficacy.
- Mathieu C, Gillard P, Benhalima K. Insulin analogues in type 1 diabetes mellitus: getting better all the time. Nature Reviews Endocrinology. 2017;13(7):385-399. doi:10.1038/nrendo.2017.39
- U.S. Food and Drug Administration. Lantus (Insulin Glargine) – Prescribing Information. FDA; 2024. Official U.S. prescribing information for insulin glargine.
Editorial Team
This article has been written and reviewed by the iMedic medical editorial team according to our strict editorial standards. Our team consists of licensed physicians, pharmacists, and medical researchers with expertise in endocrinology, diabetology, and clinical pharmacology.
Content developed by iMedic's medical writing team based on current international guidelines (WHO, EMA, FDA, ADA, EASD) and peer-reviewed endocrinological research.
Independently reviewed and fact-checked by the iMedic Medical Review Board, comprising board-certified specialists in endocrinology, diabetology, and clinical pharmacology.
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