Progesterone (Levonorgestrel)

What Is Progesterone (Levonorgestrel) and What Is It Used For?

Quick Answer: Levonorgestrel is a synthetic progestogen used primarily as emergency contraception (the morning-after pill). A single 1.5 mg tablet taken within 72 hours of unprotected intercourse prevents approximately 85% of expected pregnancies by inhibiting ovulation. It is also used in low doses for daily hormonal contraception and in intrauterine devices (IUDs).

Levonorgestrel is a second-generation synthetic progestogen — a laboratory-made compound that mimics the effects of the naturally occurring hormone progesterone in the body. Progesterone is one of the key hormones involved in the menstrual cycle, ovulation, and pregnancy. Synthetic progestogens like levonorgestrel are used in a wide range of contraceptive products because of their ability to suppress ovulation, alter the cervical mucus, and modify the endometrial lining.

When used for emergency contraception, levonorgestrel is taken as a single 1.5 mg oral dose after unprotected intercourse or contraceptive failure. The World Health Organization (WHO) classifies levonorgestrel emergency contraception as an essential medicine, and it is included on the WHO Model List of Essential Medicines. In most countries worldwide, including the United States, United Kingdom, European Union member states, Australia, and Canada, levonorgestrel emergency contraception is available without a prescription (over the counter) to individuals of reproductive age.

It is important to understand that levonorgestrel emergency contraception is not the same as an abortion pill. Levonorgestrel works by preventing or delaying ovulation — the release of an egg from the ovary. If ovulation has already occurred and fertilization and implantation have taken place, levonorgestrel will not affect the pregnancy. The medication has no abortifacient properties. This distinction has been confirmed by extensive research and is reflected in the official product labeling approved by the EMA, FDA, and WHO.

Approved Indications

Levonorgestrel is approved and used for the following indications worldwide:

• Emergency contraception (1.5 mg single dose): Used after unprotected intercourse or contraceptive failure (such as a broken or slipped condom, missed oral contraceptive pills, dislodged diaphragm, or concern about failed withdrawal). It should be taken as soon as possible, with maximum effectiveness when taken within 12 hours. It can be used up to 72 hours (3 days) after the event, though effectiveness decreases with time.
• Hormonal oral contraception (low-dose, daily use): Levonorgestrel is used in combination oral contraceptive pills (COCPs) at a dose of 150 µg combined with ethinylestradiol 30 µg, and in progestogen-only pills (POPs, also called “mini-pills”). Brand names include Yasmin (containing a different progestogen), Azalia, and Mini-Pe.
• Intrauterine system (IUS/IUD): Levonorgestrel-releasing intrauterine systems such as Kyleena provide long-acting reversible contraception by releasing small amounts of levonorgestrel directly into the uterus over 3–5 years. This reduces the total systemic hormone exposure compared to oral formulations.
• Other formulations: Levonorgestrel is also available as a long-acting injectable (Depo-Provera contains medroxyprogesterone, a related progestogen) and in implantable contraceptive rods, though the specific active ingredient may vary between these products.

How Levonorgestrel Works

The mechanism of action of levonorgestrel depends on the dose and timing of administration relative to the menstrual cycle:

• Inhibition of ovulation: The primary mechanism of emergency contraception. When taken before the luteinizing hormone (LH) surge, levonorgestrel suppresses or delays the LH peak, thereby preventing ovulation. This is the most important mechanism of action and accounts for the majority of the contraceptive effect. Studies have shown that levonorgestrel is most effective when taken in the pre-ovulatory phase of the menstrual cycle.
• Effects on sperm transport: Levonorgestrel may alter the tubal and uterine environment in ways that impair sperm transport and viability, reducing the likelihood of fertilization.
• Endometrial changes: At the low doses used in daily contraception and IUDs, levonorgestrel causes thinning and atrophy of the endometrial lining, making it less receptive to implantation. However, research suggests that this mechanism plays a minor role in emergency contraception at the 1.5 mg dose.

After oral administration of 1.5 mg levonorgestrel, peak plasma concentrations are achieved within 1–2 hours. The drug is extensively bound to plasma proteins, including sex hormone-binding globulin (SHBG) and albumin. Levonorgestrel is metabolized in the liver, primarily by CYP3A4 cytochrome enzymes, producing inactive metabolites that are excreted in approximately equal proportions via the urine and feces. The elimination half-life is approximately 26 hours, meaning that the drug is essentially cleared from the body within a few days of administration.

What Should You Know Before Taking Progesterone (Levonorgestrel)?

Quick Answer: Do not take levonorgestrel if you are allergic to it or any of its inactive ingredients. It should not be used if you are already pregnant, as it will not work. Women with severe liver disease, a history of ectopic pregnancy, or inflammatory bowel disease (e.g. Crohn’s disease) should consult a doctor before use, as the medication may be less suitable or effective.

Levonorgestrel emergency contraception is generally safe for most women of reproductive age. However, before taking it, it is important to consider whether the medication is appropriate for your individual situation. Although it is available without a prescription, understanding the contraindications, warnings, and precautions ensures safe and effective use.

Contraindications

The only absolute contraindication to levonorgestrel emergency contraception is a known allergy (hypersensitivity) to levonorgestrel or any of the inactive ingredients in the tablet. If you have previously experienced an allergic reaction to a levonorgestrel-containing product, you should not take it and should seek an alternative form of emergency contraception.

Warnings and Precautions

Talk to a doctor or pharmacist before taking levonorgestrel emergency contraception if any of the following conditions apply to you:

• Previous ectopic pregnancy: If you have previously had a pregnancy that developed outside the uterus (ectopic pregnancy), the risk of a subsequent ectopic pregnancy is increased. While levonorgestrel does not cause ectopic pregnancy, if it fails to prevent pregnancy, the resulting pregnancy may be ectopic. Seek medical attention immediately if you experience severe lower abdominal pain after taking the medication, especially if your period is late.
• Previous salpingitis (fallopian tube inflammation): A history of fallopian tube inflammation increases the risk of ectopic pregnancy, and you should be monitored if you take emergency contraception.
• Inflammatory bowel disease (e.g. Crohn’s disease): Severe intestinal disease may impair the absorption of levonorgestrel from the gastrointestinal tract, potentially reducing its effectiveness. Alternative emergency contraception (such as a copper IUD) may be more appropriate.
• Severe liver disease: Levonorgestrel is metabolized in the liver, and severe hepatic impairment may alter its metabolism and clearance. Consult a doctor before use.
• Menstrual status: Levonorgestrel is not intended for use before the first menstrual period (menarche). It can be used at any point during the menstrual cycle, provided you are not already pregnant.

Body Weight and Effectiveness

There is some evidence suggesting that levonorgestrel emergency contraception may be less effective in women with higher body weight or body mass index (BMI). A pharmacokinetic analysis showed that peak plasma concentrations of levonorgestrel are lower in women with higher body weight, which could theoretically reduce the medication’s ability to suppress ovulation. However, the available clinical data on this issue are limited and inconclusive.

In 2014, the European Medicines Agency (EMA) reviewed the available evidence and concluded that the benefits of levonorgestrel emergency contraception outweigh the risks for all women, regardless of body weight. The WHO and ACOG have similarly recommended that levonorgestrel should be offered to all women who need emergency contraception, irrespective of BMI. Women who are concerned about efficacy can discuss alternative options with a healthcare provider, including ulipristal acetate (ellaOne, effective up to 120 hours) or a copper intrauterine device (the most effective form of emergency contraception).

Pregnancy and Breastfeeding

Pregnancy

Levonorgestrel emergency contraception should not be taken if you are already pregnant, as it will not work. However, if you take levonorgestrel not knowing that you are already pregnant, or if the medication fails and pregnancy occurs, current evidence indicates that levonorgestrel does not harm the developing fetus. There is no evidence of teratogenic effects (birth defects) or adverse pregnancy outcomes associated with levonorgestrel exposure during early pregnancy. Nevertheless, if you become pregnant after taking the medication, you should see a doctor to confirm that the pregnancy is developing normally and to rule out an ectopic pregnancy.

Breastfeeding

Levonorgestrel is excreted into breast milk in small amounts. To minimize the infant’s exposure, it is recommended that you take the tablet immediately after a breastfeeding session and then avoid breastfeeding for at least 8 hours. During this 8-hour period, express and discard breast milk using a breast pump. This approach ensures that you take the medication promptly (timing is critical for effectiveness) while minimizing the amount of levonorgestrel transferred to the infant through breast milk.

Sexually Transmitted Infections

Levonorgestrel emergency contraception does not provide any protection against sexually transmitted infections (STIs), including HIV/AIDS. Only barrier methods such as condoms offer protection against STIs. If a condom was not used during intercourse (or if it broke or slipped), there may be a risk of STI exposure. Consult a healthcare provider if you have concerns about potential STI transmission.

Fertility

Levonorgestrel emergency contraception does not have any long-term effect on fertility. After taking the medication, ovulation may occur slightly earlier or later than expected in the current menstrual cycle, which can temporarily alter the timing of your fertile days. However, normal fertility is expected to return rapidly, and regular contraception should be used or resumed as soon as possible after taking emergency contraception. There are no long-term data suggesting that levonorgestrel impairs future fertility.

Driving and Operating Machinery

Levonorgestrel is unlikely to affect your ability to drive or operate machinery. However, some women may experience fatigue or dizziness after taking the medication. If you are affected, avoid driving or operating machinery until these symptoms have resolved.

How Does Progesterone (Levonorgestrel) Interact with Other Drugs?

Quick Answer: Several medications can significantly reduce the effectiveness of levonorgestrel emergency contraception, including anti-epileptic drugs (phenytoin, carbamazepine, phenobarbital), anti-tuberculosis drugs (rifampicin, rifabutin), some HIV treatments (ritonavir, efavirenz), the antifungal griseofulvin, and the herbal supplement St. John’s Wort. If you have used any of these in the past 4 weeks, consult a healthcare provider — a double dose or alternative emergency contraception may be needed.

Levonorgestrel is metabolized by the liver enzyme CYP3A4. Drugs that induce (speed up) this enzyme can increase the rate at which levonorgestrel is broken down, leading to lower blood levels and potentially reduced contraceptive effectiveness. This is a clinically significant interaction that can result in unintended pregnancy.

If you have used any of the following medications within the past 4 weeks, levonorgestrel emergency contraception may be less effective. Your doctor or pharmacist may recommend one of the following alternatives: a double dose of levonorgestrel (i.e. two 1.5 mg tablets taken at the same time, totaling 3 mg), ulipristal acetate (ellaOne), or a copper intrauterine device (IUD), which is not affected by enzyme-inducing drugs and is the most effective emergency contraceptive available.

Effect of Levonorgestrel on Other Medications

Levonorgestrel can also affect the metabolism of other drugs. One notable interaction involves ciclosporin (cyclosporine), an immunosuppressant medication used to prevent organ transplant rejection and treat certain autoimmune conditions. Levonorgestrel may inhibit the metabolism of ciclosporin, potentially increasing ciclosporin blood levels and the risk of toxicity. If you are taking ciclosporin, inform your doctor or pharmacist before taking levonorgestrel emergency contraception.

Regular Hormonal Contraception

If you are already using a regular hormonal contraceptive (such as the combined oral contraceptive pill, a progestogen-only pill, a contraceptive patch, or a vaginal ring), you can take levonorgestrel emergency contraception and then continue with your regular method at the usual times. However, it is important to understand that the emergency contraceptive does not provide ongoing protection — you must continue your regular method and use a barrier method (such as condoms) until your regular contraception is fully effective again. Consult your doctor or pharmacist for specific guidance on when full contraceptive protection is restored.

What Is the Correct Dosage of Progesterone (Levonorgestrel)?

Quick Answer: For emergency contraception, take one 1.5 mg tablet as soon as possible after unprotected intercourse, ideally within 12 hours and no later than 72 hours (3 days). Swallow the tablet whole with water. If you are taking enzyme-inducing medications, a double dose (3 mg) may be recommended. If you vomit within 3 hours, take another tablet.

Emergency Contraception (Standard Dose)

Children

Levonorgestrel emergency contraception is not recommended for use before the first menstrual period (menarche). There is limited data on its use in adolescents under 16 years of age. In adolescents who have reached menarche, the same dose and administration instructions apply as for adults. Healthcare providers should be consulted for guidance in younger adolescents.

Elderly

Levonorgestrel emergency contraception is indicated for women of reproductive age and is not relevant for postmenopausal women.

If You Vomit After Taking the Tablet

If you vomit within 3 hours of taking the tablet, the medication may not have been fully absorbed. Take another 1.5 mg tablet immediately. If you continue to vomit, consult a healthcare provider, as alternative emergency contraception (such as a copper IUD) may be more appropriate.

Overdose

There are no reports of serious adverse effects from taking more than the recommended dose of levonorgestrel. If you have accidentally taken several tablets at once, you may experience nausea, vomiting, or vaginal bleeding. No specific antidote is required. If you are concerned, or if a child has accidentally ingested the medication, contact a healthcare provider or poison control center for advice.

After Taking Levonorgestrel

After taking levonorgestrel emergency contraception, it is essential to resume or initiate regular contraception as soon as possible. The emergency contraceptive provides protection only against the single episode of unprotected intercourse for which it was taken. If you have further unprotected intercourse after taking the tablet — even within the same menstrual cycle — you are at risk of pregnancy again, as the tablet does not provide ongoing contraceptive protection.

You should use a barrier method (such as condoms or a diaphragm with spermicide) until your next menstrual period. Approximately 3 weeks after taking levonorgestrel, consult a healthcare provider or take a pregnancy test to confirm that the medication was effective. Contact a doctor as soon as possible if your period is more than 5 days late, or if bleeding at the expected time of your period is unusually light or heavy.

Frequency of Use

Levonorgestrel emergency contraception is intended for occasional, emergency use only. It should not be used as a regular method of contraception. Using it more than once within the same menstrual cycle is not recommended, as this increases the likelihood of menstrual cycle disruption and reduces the reliability of the medication. If you find that you need emergency contraception frequently, discuss long-term contraceptive options with a healthcare provider, as methods such as hormonal IUDs, implants, or daily oral contraceptives are far more effective at preventing pregnancy than emergency contraception.

What Are the Side Effects of Progesterone (Levonorgestrel)?

Quick Answer: The most common side effects of levonorgestrel emergency contraception include nausea (very common), lower abdominal pain, fatigue, headache, and irregular vaginal bleeding. Some women may also experience vomiting, diarrhea, breast tenderness, dizziness, and changes to their next menstrual period. Most side effects are mild and resolve within a few days without treatment.

Like all medicines, levonorgestrel can cause side effects, although not everyone experiences them. The side effects of levonorgestrel emergency contraception are generally mild and short-lived. They are related to the pharmacological action of the high-dose progestogen and typically resolve within 24–48 hours. The following frequency categories are based on data from clinical trials and post-marketing surveillance.

Menstrual Changes After Emergency Contraception

After taking levonorgestrel emergency contraception, most women will have their next menstrual period at the expected time. However, some women may notice that their period arrives a few days earlier or later than usual. The bleeding may be heavier or lighter than normal, or you may experience spotting or irregular bleeding before your next period. These changes are temporary and are caused by the high-dose progestogen effect on the endometrial lining.

If your period is more than 5 days late, or if the bleeding at the time of your expected period is abnormally light or heavy, you should take a pregnancy test to rule out the possibility that the emergency contraceptive did not work. Contact a healthcare provider if you are concerned about any menstrual changes.

When to Seek Medical Attention

Although serious side effects from levonorgestrel emergency contraception are extremely rare, you should seek immediate medical attention in the following situations:

• Severe abdominal pain: Especially if it occurs several days or weeks after taking the medication and is accompanied by a late period. This could be a sign of an ectopic pregnancy, which requires urgent medical evaluation.
• Signs of an allergic reaction: Including rash, hives, itching, swelling of the face, lips, tongue, or throat, and difficulty breathing or swallowing. Seek emergency medical care immediately.
• Persistent or heavy bleeding: If vaginal bleeding is much heavier than normal or does not stop, consult a healthcare provider.

How Should You Store Progesterone (Levonorgestrel)?

Quick Answer: Store levonorgestrel tablets at room temperature, below 25°C (77°F), in the original packaging. Keep out of the reach of children. Do not use after the expiry date printed on the packaging. Dispose of unused or expired medication through a pharmacy — do not flush down the toilet or throw in household waste.

Levonorgestrel tablets should be stored in their original blister packaging to protect them from moisture and light. No special storage conditions are required beyond standard room temperature (below 25°C / 77°F). Do not refrigerate or freeze the medication.

Keep the medication out of the sight and reach of children. If you keep emergency contraception at home “just in case,” ensure it is stored in a secure location where children cannot access it. Check the expiry date before taking the medication — the expiry date is printed on the blister pack and outer carton after “EXP.” The expiry date refers to the last day of that month.

Do not dispose of medicines in the wastewater or household waste. Take any unused or expired medication to a pharmacy for safe disposal. This helps protect the environment from pharmaceutical contamination.

What Does Progesterone (Levonorgestrel) Contain?

Quick Answer: Each tablet contains 1.5 mg of levonorgestrel as the active ingredient. Inactive ingredients include microcrystalline cellulose, lactose monohydrate, croscarmellose sodium, poloxamer, and magnesium stearate. The tablet is round, white, biconvex, and 6 mm in diameter.

Active Ingredient

The active substance is levonorgestrel. Each tablet contains 1.5 mg of levonorgestrel. Levonorgestrel is a synthetic progestogen (a laboratory-made compound that mimics the effects of the naturally occurring hormone progesterone). It is one of the most widely studied and used progestogens in hormonal contraception worldwide.

Inactive Ingredients (Excipients)

The inactive ingredients in levonorgestrel 1.5 mg tablets vary slightly between manufacturers, but typically include:

• Microcrystalline cellulose: A bulking agent that provides the tablet with its structure and aids in disintegration.
• Lactose monohydrate: A filler derived from milk sugar. If you have been told by a doctor that you have an intolerance to certain sugars (including lactose), contact your doctor before taking this medication.
• Croscarmellose sodium: A disintegrant that helps the tablet break apart in the stomach for faster absorption.
• Poloxamer: A surfactant that aids in the dissolution and absorption of the active ingredient.
• Magnesium stearate: A lubricant used in the manufacturing process to prevent the tablet from sticking to machinery.

Physical Appearance

Levonorgestrel 1.5 mg emergency contraception tablets are typically round, white, biconvex (slightly curved on both sides), approximately 6 mm in diameter, and may bear identification markings depending on the manufacturer. Each blister pack contains one tablet.

Available Formulations and Brands

Levonorgestrel is available under numerous brand names worldwide, reflecting its widespread use in different contraceptive formulations:

• Emergency contraception (1.5 mg tablet): Sold as Plan B One-Step, Levonelle, NorLevo, Postinor, and numerous generic equivalents.
• Progestogen-only pill (mini-pill): Azalia, Mini-Pe, Norgeston, Microval.
• Levonorgestrel-releasing IUS: Kyleena (19.5 mg, releasing 17.5 µg/day initially), Mirena (52 mg, releasing 20 µg/day initially), Jaydess/Skyla.
• Other formulations: Crinone (progesterone gel, not levonorgestrel), Depo-Provera (medroxyprogesterone acetate injection), Prolutex (progesterone injection), Cyclogest (progesterone suppositories). Note: these products contain different progestogens but belong to the same broader pharmacological class.

References and Sources

All information in this article is based on peer-reviewed medical literature, international clinical guidelines, and regulatory authority product information. The following sources were used:

1. World Health Organization (WHO). Selected Practice Recommendations for Contraceptive Use. 3rd edition, 2016 (updated 2023). WHO Essential Medicines List.
2. European Medicines Agency (EMA). Summary of Product Characteristics: Levonorgestrel 1.5 mg Emergency Contraception. 2024.
3. Faculty of Sexual & Reproductive Healthcare (FSRH). FSRH Clinical Guideline: Emergency Contraception. 2023 update.
4. American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin No. 152: Emergency Contraception. Updated 2023.
5. Gemzell-Danielsson K, et al. Mechanism of action of levonorgestrel for emergency contraception. Contraception. 2013;87(3):300–308. doi:10.1016/j.contraception.2012.09.014.
6. Glasier A, et al. Ulipristal acetate versus levonorgestrel for emergency contraception: a randomised non-inferiority trial and meta-analysis. Lancet. 2010;375(9714):555–562.
7. National Institute for Health and Care Excellence (NICE). Contraception: Emergency contraception. CKS. 2024.
8. Cleland K, et al. The efficacy of intrauterine devices for emergency contraception: a systematic review of 35 years of experience. Human Reproduction. 2012;27(7):1994–2000.
9. British National Formulary (BNF). Levonorgestrel. 2025.
10. U.S. Food and Drug Administration (FDA). Plan B One-Step Label. Approved product information. 2024.

Editorial Team

This article was researched and written by the iMedic Medical Editorial Team, a group of licensed specialist physicians with expertise in clinical pharmacology, reproductive medicine, and gynecology. All content is reviewed according to international guidelines (WHO, EMA, FDA, FSRH, ACOG, BNF) and follows the GRADE evidence framework.