Protaphane InnoLet: Uses, Dosage & Side Effects

What Is Protaphane InnoLet and What Is It Used For?

Protaphane is a brand of isophane human insulin, an intermediate-acting insulin preparation also widely known as NPH insulin (Neutral Protamine Hagedorn). The active ingredient is human insulin produced by recombinant DNA technology in Saccharomyces cerevisiae (baker's yeast), structurally identical to the insulin naturally secreted by the human pancreas. In Protaphane, the insulin molecules are crystallised with protamine sulfate and zinc, forming microscopic crystals that dissolve slowly after subcutaneous injection. This crystalline formulation is what gives Protaphane its characteristic cloudy, milky-white appearance and its prolonged duration of action compared to clear, soluble human insulin.

InnoLet is the name of the delivery device: a disposable pre-filled pen manufactured by Novo Nordisk, purpose-built for patients who may find traditional insulin pens or syringes challenging. Its distinctive features include a large, rotating dose-selector knob with high-contrast numbers, audible and tactile clicks for each unit of insulin, a clearly visible dose window, and an ergonomic grip. These characteristics make the InnoLet particularly useful for older adults, people with arthritis, those with tremor or neuropathy, and patients with reduced visual acuity. Once all the insulin has been used, the entire pen is discarded as sharps waste and a new pen is started; there is no cartridge to replace.

Diabetes mellitus is a chronic metabolic disease defined by sustained elevation of blood glucose due to defects in insulin production, insulin action, or both. In type 1 diabetes, autoimmune destruction of pancreatic beta cells causes complete insulin deficiency, requiring lifelong exogenous insulin replacement from the time of diagnosis. In type 2 diabetes, progressive insulin resistance combined with declining beta-cell function leads many patients eventually to require insulin therapy, particularly when oral agents and non-insulin injectables no longer achieve adequate glycaemic targets. Protaphane can be used in both types of diabetes, as well as in gestational diabetes when insulin treatment is indicated during pregnancy.

Protaphane provides basal insulin coverage, meaning it delivers a slow, steady release of insulin over many hours to match the body's ongoing (non-mealtime) insulin needs. Between meals and overnight, the liver continuously releases glucose into the bloodstream, and basal insulin is required to suppress this hepatic glucose output and maintain blood sugar within target range. In a typical treatment regimen, Protaphane is injected once or twice daily — most commonly in the evening (often at bedtime) or as split morning and evening doses — and is frequently paired with a short-acting or rapid-acting insulin (such as human soluble insulin or insulin aspart) administered before main meals. This combination, called a basal-bolus regimen, mimics the natural pattern of insulin secretion in people without diabetes.

Although modern long-acting insulin analogues such as insulin glargine (Lantus, Toujeo), insulin detemir (Levemir), and insulin degludec (Tresiba) have become first-line basal insulins in many high-income settings due to their flatter pharmacokinetic profiles and reduced risk of nocturnal hypoglycemia, isophane NPH insulin remains an essential, cost-effective, and widely prescribed option worldwide. According to the International Diabetes Federation, approximately 537 million adults are currently living with diabetes, projected to rise to 643 million by 2030 and 783 million by 2045. Human NPH insulin, including Protaphane, is included on the WHO Model List of Essential Medicines, reflecting its central role in diabetes care in both high- and low-income healthcare systems. The InnoLet device format has particular value for elderly patients, vision-impaired patients, and anyone who needs reliable, low-complexity dosing.

What Should You Know Before Taking Protaphane InnoLet?

Protaphane is a prescription-only medicine that should be initiated under the supervision of a doctor experienced in diabetes management. Before your first injection, your healthcare team will provide hands-on training in injection technique, blood glucose monitoring, carbohydrate counting, hypoglycemia recognition and treatment, and sick-day rules. Never start, change, or stop insulin therapy without medical supervision.

Contraindications

You should not use Protaphane InnoLet in the following circumstances:

• Allergy: If you are allergic (hypersensitive) to human insulin or any of the other ingredients in Protaphane (protamine sulfate, zinc chloride, glycerol, metacresol, phenol, disodium phosphate dihydrate, sodium hydroxide, hydrochloric acid, or water for injections).
• Hypoglycemia: If you feel the onset of hypoglycemia (low blood sugar symptoms such as sweating, trembling, rapid heartbeat, confusion, or dizziness), do not inject additional insulin until the episode is treated and blood sugar has returned to a safe level.
• Insulin pumps: Protaphane must never be used in continuous subcutaneous insulin infusion (CSII) pumps. The suspension will block the catheter and deliver insulin unpredictably.
• Intravenous or intramuscular use: Protaphane must never be injected into a vein or muscle. It is designed exclusively for subcutaneous (under-the-skin) injection. Intravenous administration of NPH insulin could cause severe, rapid hypoglycemia.
• Damaged device: If the InnoLet pen has been dropped, crushed, or shows visible damage, it must not be used.
• Improper storage: If the insulin has been frozen at any point, it must be discarded even if it appears unchanged after thawing.
• Abnormal appearance: If after thorough mixing the suspension does not appear uniformly white and cloudy, or if lumps or white particles remain on the side or bottom of the cartridge, do not use the pen.

Warnings and Precautions

Discuss the following important considerations with your healthcare provider before and during treatment with Protaphane InnoLet:

• Kidney, liver, or endocrine problems: Impaired kidney function, liver disease, or disorders of the adrenal, pituitary, or thyroid glands can significantly alter insulin requirements. Your dose may need adjustment and more frequent blood glucose monitoring is recommended.
• Physical activity: Exercise typically increases insulin sensitivity and lowers blood sugar. Substantial changes in activity levels may require a reduction in insulin dose or additional carbohydrate intake before, during, or after exertion.
• Dietary changes: Shifting carbohydrate intake (skipping meals, fasting for religious observance, low-carbohydrate diets, or bariatric surgery) can profoundly affect insulin needs. Discuss any dietary changes with your diabetes team before implementing them.
• Intercurrent illness: During infections, fever, trauma, or surgery, insulin requirements often rise — sometimes dramatically — even when appetite is reduced. Continue insulin and follow agreed sick-day rules; test blood glucose (and ketones if you have type 1 diabetes) more frequently and contact your healthcare provider if readings are persistently high or if you cannot keep food or fluids down.
• International travel and time zones: Crossing time zones may require temporary dose timing adjustments to maintain steady basal coverage. Plan ahead with your doctor, carry prescriptions and a letter confirming your diagnosis, and pack insulin in hand luggage to avoid freezing in aircraft holds.
• Switching insulin types or brands: Changing from another insulin preparation to Protaphane (or vice versa) must be done under medical supervision, as dose and timing may differ significantly between products. Small differences in absorption can lead to unexpected hypoglycemia or hyperglycemia.
• Hypoglycemia unawareness: With long-standing diabetes or frequent low blood sugar episodes, warning symptoms of hypoglycemia (trembling, sweating, palpitations) may become blunted or absent. If you experience this, discuss strategies with your doctor, such as raising blood glucose targets temporarily or using continuous glucose monitoring.

Pregnancy and Breastfeeding

If you are pregnant, believe you may be pregnant, or are planning to become pregnant, speak with your doctor before using Protaphane. Isophane human insulin is considered safe and effective in pregnancy — in fact, insulin (including NPH) is the preferred treatment for diabetes during pregnancy because it does not cross the placenta in meaningful amounts and has an extensive track record of safety in both mother and baby. Tight blood glucose control during pregnancy is essential to minimise the risk of complications including pre-eclampsia, macrosomia (excessive fetal growth), congenital malformations, preterm birth, and neonatal hypoglycemia.

Insulin requirements change throughout pregnancy. In the first trimester, insulin sensitivity may briefly increase, transiently reducing insulin needs and raising the risk of hypoglycemia. From the second trimester onward, placental hormones (human placental lactogen, cortisol, progesterone) create substantial insulin resistance, and total daily insulin requirements often rise by 50–100% by the third trimester. Following delivery, insulin needs typically fall sharply within hours and may temporarily drop below pre-pregnancy levels, requiring prompt dose reduction. Frequent contact with your diabetes antenatal team, pre-conception counselling, and regular fetal and maternal monitoring are essential.

Breastfeeding does not restrict the use of Protaphane. Exogenous insulin is a large protein that is not absorbed intact from breast milk and poses no known risk to the nursing infant. However, lactation itself lowers blood glucose, and insulin dose may need to be reduced during breastfeeding. Eating a carbohydrate-containing snack before or during feeding, and monitoring blood glucose frequently, can help prevent nursing-related hypoglycemia.

Use in Children and Adolescents

Protaphane can be used in children and adolescents of all ages with diabetes requiring insulin therapy. Dosing must be individually titrated by a paediatric endocrinologist, taking into account age, weight, pubertal stage, eating patterns, physical activity, and growth. Insulin requirements vary considerably during childhood and adolescence, with marked increases during the pubertal growth spurt driven by rising levels of growth hormone and sex steroids. Parents and caregivers must be thoroughly trained in injection technique, hypoglycemia recognition and treatment, and in recognising signs of diabetic ketoacidosis. School nurses and teachers should also be informed where appropriate.

Use in Elderly Patients

The InnoLet device was designed with older users in mind. Its oversized, high-contrast dose dial, audible clicks per unit, and ergonomic grip make dose selection and injection significantly easier for patients with reduced vision, arthritis, or mild dexterity issues. Nevertheless, older adults are at greater risk of hypoglycemia, with consequences that can be severe — falls, fractures, cardiac events, and cognitive impairment. Glycaemic targets may be individualised to be less strict in frail older patients, and carers should be involved in monitoring where appropriate.

Driving and Operating Machinery

Both hypoglycemia and hyperglycemia can impair concentration, reaction time, and judgement, placing you and others at risk when driving or operating heavy machinery. Before every drive, check your blood glucose and avoid driving if it is low or if you have recently experienced hypoglycemia. Always carry rapid-acting glucose in the vehicle. If you experience hypoglycemia unawareness or frequent low readings, speak with your doctor about whether it is safe to drive, as many jurisdictions require notification of the driving authority and a medical review before returning to the road.

Sodium Content

Protaphane InnoLet contains less than 1 mmol sodium (23 mg) per dose, and is considered essentially sodium-free. This is relevant for patients on a controlled sodium diet.

How Does Protaphane InnoLet Interact with Other Drugs?

Drug interactions with insulin are clinically important because they can make blood glucose either too low or too high, sometimes in unpredictable ways. Careful review of concomitant medications, close blood glucose monitoring, and proactive dose adjustment are essential whenever any new medicine is started, stopped, or its dose is changed. Below is a structured overview of the most important interactions, grouped by their net effect on blood sugar.

Major Interactions: Drugs That Lower Blood Sugar

The following medications can enhance Protaphane's blood-glucose-lowering effect. When combined with insulin, they increase the risk of hypoglycemia, and closer monitoring or dose reduction may be needed:

Minor and Counter-Regulatory Interactions: Drugs That Raise Blood Sugar

The following medicines can counteract insulin's effect and push blood glucose upward. Starting such a medicine during ongoing Protaphane therapy commonly requires an insulin dose increase, and stopping it may require a dose reduction:

Medicines with Variable or Unpredictable Effects

Octreotide and lanreotide, used for acromegaly and neuroendocrine tumours, can raise or lower blood glucose depending on dose, duration, and the patient's underlying metabolic state; meticulous glucose monitoring is required when these are started, stopped, or dose-adjusted. Beta-blockers warrant special attention because, in addition to enhancing hypoglycemia, they can mask the classic adrenergic warning signs (tremor, palpitations), often leaving sweating as the only residual warning symptom. If you take a beta-blocker, you may need to rely on blood glucose monitoring rather than symptoms to detect low blood sugar.

Pioglitazone used together with insulin has been associated with an increased risk of heart failure, particularly in patients with long-standing type 2 diabetes and pre-existing cardiac disease. If you take pioglitazone alongside Protaphane, report any unexplained shortness of breath, rapid weight gain, or leg swelling promptly. Pentamidine, used to treat pneumocystis pneumonia, can cause hypoglycemia followed by hyperglycemia due to beta-cell toxicity.

Alcohol

Alcohol has complex, biphasic effects on blood glucose. Sugar-containing drinks (sweet wines, liqueurs, mixers) may initially raise blood sugar, whereas alcohol itself impairs hepatic gluconeogenesis, causing a delayed and prolonged fall in blood glucose that may occur several hours after drinking or overnight. Alcohol also impairs the recognition of hypoglycemia and may resemble intoxication, delaying appropriate treatment. If you choose to drink, do so in moderation, always eat carbohydrate alongside alcohol, check blood glucose before bed, and inform those around you of the signs of hypoglycemia.

What Is the Correct Dosage of Protaphane InnoLet?

There is no single universal dose of Protaphane — treatment must be tailored to the individual by a clinician experienced in insulin therapy. Your starting dose depends on factors such as your body weight, whether you are newly diagnosed or transitioning from another insulin, your carbohydrate intake, exercise habits, other diabetes medications, and concurrent illnesses. Typical total daily insulin requirements in established type 1 diabetes are approximately 0.5–1.0 units per kilogram of body weight per day, with basal insulin like Protaphane generally contributing about 40–50% of the total. In type 2 diabetes, starting basal insulin doses are often lower (for example, 10 units once daily or 0.1–0.2 units/kg/day), titrated upward based on fasting blood glucose.

Adults

Children and Adolescents

Elderly Patients

Kidney or Liver Impairment

Insulin is metabolised by both the liver and kidneys. In significant hepatic or renal impairment, insulin clearance is reduced, resulting in lower insulin requirements and a higher risk of hypoglycemia. More frequent blood glucose monitoring and stepwise dose reduction are typical approaches. Particular caution is required in end-stage renal disease and in patients on dialysis, where insulin needs may fluctuate markedly around dialysis sessions.

How and Where to Inject

Protaphane InnoLet is injected subcutaneously (under the skin) only. It must never be injected intravenously (into a vein) or intramuscularly (into a muscle), as this would dramatically alter its absorption profile and could cause rapid, severe hypoglycemia.

The recommended injection sites include:

• Front of thighs: A common and convenient site with relatively slow absorption, well suited to basal insulin.
• Abdomen (at least 2–5 cm from the navel): Faster absorption than the thigh. Note that mixing absorption sites (abdomen for rapid-acting insulin, thigh for basal) is often preferred.
• Buttocks (upper outer quadrant): Reliable absorption, particularly useful for NPH insulin.
• Upper arms (lateral): Possible but may be awkward to self-inject; typically used if a carer performs the injection.

Rotate injection sites systematically within the same body region at each injection to prevent lipodystrophy. Use a new needle for every injection — re-using needles increases the risk of bent or blocked tips, inaccurate dosing, infection, and lipohypertrophy. After inserting the needle, press the injection button fully and hold it down for at least 6 seconds before removing the needle, to ensure the complete dose is delivered. Remove and dispose of the needle in a sharps container after each injection — never store the pen with a needle attached.

Missed Dose

If you realise shortly after the usual injection time that you have missed a dose of Protaphane, inject it as soon as possible and continue with your usual dose schedule. If it is closer to the next scheduled dose, skip the missed dose and resume normal dosing — do not double up. A missed basal insulin dose typically results in gradually rising blood sugars; check your blood glucose more frequently for the next 24 hours and contact your diabetes team if readings remain elevated or if ketones develop (in type 1 diabetes).

Overdose

If you accidentally inject too much Protaphane, your blood sugar may drop to dangerously low levels (hypoglycemia). Because NPH has a prolonged and peaked profile, hypoglycemia from an overdose may be delayed by several hours and can be prolonged; monitoring for 12–24 hours is prudent. For mild hypoglycemia, consume 15–20 g of fast-acting carbohydrate (glucose tablets, fruit juice, sugar-sweetened drinks), recheck blood glucose after 15 minutes, and repeat if still low. Follow up with a longer-acting snack or meal to prevent recurrence. For severe hypoglycemia with confusion, seizures, or unconsciousness, a companion must administer a glucagon injection (or nasal glucagon) and call emergency services immediately. Never give food or drink to an unconscious person. After any episode, review the cause and dose with your doctor.

What Are the Side Effects of Protaphane InnoLet?

As with all medicines, Protaphane can cause side effects, though not everyone experiences them. Because NPH insulin has a peaked profile, the most important and frequent adverse effect is hypoglycemia, which can occur several hours after injection — often overnight when given as an evening dose. The side effects listed below are classified according to internationally accepted pharmacovigilance frequency categories.

Recognising and Managing Hypoglycemia

Because hypoglycemia is the most important side effect of Protaphane, understanding how to recognise and manage it is essential for every person using insulin and for family, friends, and carers who may need to intervene:

Make sure people around you — family, friends, colleagues, teachers — know that you have diabetes, that you use insulin, and what to do if you become unwell. A medical identification bracelet or necklace can be lifesaving if you are found unresponsive. Keep a glucagon kit at home and at work or school if you are at high risk of severe hypoglycemia.

Recognising and Managing Hyperglycemia

Hyperglycemia (high blood sugar) can occur if too little insulin has been injected, if you miss a dose, during illness, after high-carbohydrate meals, with reduced physical activity, or if insulin has been stored incorrectly. Early warning signs develop over hours to days and include increased thirst, frequent urination, tiredness, dry skin and mouth, loss of appetite, blurred vision, and nausea. Untreated, hyperglycemia can progress to diabetic ketoacidosis with acetone-smelling breath, rapid deep breathing (Kussmaul respiration), vomiting, abdominal pain, and drowsiness — a medical emergency. If blood glucose is persistently above target, check for ketones (especially in type 1 diabetes), hydrate with sugar-free fluids, and contact your diabetes team or seek emergency care as advised.

How Should You Store Protaphane InnoLet?

Correct storage of insulin is essential for maintaining its potency. Insulin that has been stored improperly may lose biological activity without any obvious visual change, resulting in unexplained hyperglycemia and unpredictable blood sugar control. Follow these guidelines to keep your Protaphane InnoLet safe and effective.

Unused Pens (Not Yet in Use)

• Store in a refrigerator at 2–8°C, ideally in the main compartment, not in the door (where temperature fluctuates) and not directly against the back wall (which can be the coldest area).
• Do not freeze. Frozen insulin is irreversibly damaged and must be discarded, even after thawing.
• Do not store near the freezer compartment.
• Keep pens in their outer carton to protect from light.
• Check the expiry date (EXP) before use — the expiry date refers to the last day of the printed month.

In Use or Carried as a Spare

• Store at room temperature, up to 30°C.
• Do not refrigerate or freeze a pen that is already in use.
• Keep in use for a maximum of 6 weeks. After 6 weeks, discard the pen even if insulin remains — both the preservative and the insulin can lose effectiveness over time at room temperature.
• Protect from direct sunlight and excessive heat (e.g. do not leave in a hot car, near a radiator, or on a windowsill).
• Replace the pen cap after each use to protect from light and mechanical damage.
• Keep out of the sight and reach of children.

Travel Storage

When travelling, always carry insulin in hand luggage, never in the aircraft hold (where temperatures may fall below freezing). Use an insulated travel pouch with gel packs (keeping the insulin near but not in direct contact with frozen ice) or a cooling wallet rated for medicines. In very hot climates, plan refrigeration where possible and keep insulin out of the sun. Carry a doctor's letter and a copy of your prescription to explain needles and medical equipment at customs.

Disposal

Used needles and empty pens must be disposed of as sharps waste. Use an approved sharps container and return it to a pharmacy, GP surgery, or authorised collection point for safe disposal according to local regulations. Never put sharps in household waste or recycling bins, and never dispose of medicines down the toilet or sink. Ask your pharmacist for advice on local disposal schemes.

What Does Protaphane InnoLet Contain?

Active Ingredient

The active substance is isophane human insulin (human insulinum isophanum), also known as NPH insulin. Each millilitre of suspension contains 100 IU (international units) of insulin. Each InnoLet pre-filled pen contains 3 ml, providing a total of 300 IU per pen. The human insulin in Protaphane is produced by recombinant DNA technology in Saccharomyces cerevisiae (baker's yeast) and is structurally identical to the insulin produced naturally by the human pancreas, ensuring high purity and minimal immunogenicity compared to older animal-derived insulin preparations.

In Protaphane, the insulin molecules are crystallised with protamine sulfate and zinc to form small microcrystals. After subcutaneous injection, these crystals dissolve gradually, releasing insulin into the bloodstream over many hours. This mechanism gives Protaphane its intermediate-acting profile and its characteristic cloudy white appearance — the crystals must be resuspended before every injection to ensure a consistent dose.

Inactive Ingredients (Excipients)

Protaphane InnoLet contains less than 1 mmol sodium (23 mg) per dose, meaning it is essentially sodium-free. This is generally not clinically significant even in patients on controlled sodium diets.

Available Forms and Pack Sizes

Protaphane InnoLet is supplied as a cloudy, white suspension for injection in 3 ml disposable pre-filled pens (InnoLet), each containing 300 IU of isophane human insulin. The pens are packaged in cartons of 1, 5, or 10 pens. Not all pack sizes may be available in every country. InnoLet pens are designed for use with NovoFine or NovoTwist disposable injection needles. The pen's key design features include:

• A large, rotating dose dial with high-contrast black numbers on a white background
• A dose selector that can be corrected if set too high, without wasting insulin
• Audible and tactile clicks for each single unit, supporting non-visual dose setting
• An ergonomic, slightly angled grip that is easier to hold for people with arthritis or reduced grip strength
• A clear dose window for visual confirmation

Manufacturer

Protaphane InnoLet is manufactured by Novo Nordisk A/S, Novo Allé, DK-2880 Bagsværd, Denmark. Novo Nordisk is a global leader in diabetes care with over a century of experience in insulin development, production, and device design. The specific manufacturing site is identified by the batch number printed on the carton and pen label.