Progestogen (POP / IUS / emergency contraception) Pregnancy: Not to be given in pregnancy and will not interrupt an existing pregnancy; limited data indicate no adverse fetal effects if pregnancy continues. Excreted in breast milk - to reduce infant exposure, take immediately after a feed and avoid nursing for at least 8 hours after the dose.

Levonorgestrel

Brand names: Mirena, Levosert, Jaydess, Kyleena, Levonelle

Levonorgestrel, a synthetic progestogen, used in gynaecology for emergency contraception, within combined and progestogen-only contraceptive products, and in intrauterine systems for contraception and menstrual management.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 1.5 mg (one tablet)

Route: oral

Frequency: single dose

Emergency contraception (UK SPC, Levonorgestrel 1.5 mg tablets). Take one 1.5 mg tablet as soon as possible, preferably within 12 hours and no later than 72 hours after unprotected intercourse. If vomiting occurs within 3 hours, take another tablet immediately. Women who have used enzyme-inducing drugs in the last 4 weeks and need emergency contraception should use a non-hormonal method (Cu-IUD), or take a double dose (2 tablets = 3 mg together) if unable or unwilling to use a Cu-IUD. May be used at any point in the menstrual cycle unless menstrual bleeding is overdue. Advise a barrier method until the next period. Does not contraindicate continuation of regular hormonal contraception; repeated use within one cycle is not advisable. Efficacy may be reduced with increasing body weight/BMI (limited, inconclusive data). Note: the US bundle in this source is a different product (levonorgestrel with ethinylestradiol extended-cycle combined oral contraceptive, 'Iclevia') and was not used for this emergency-contraception dose.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to levonorgestrel or to any of the excipients

Side effects

Nausea (most common)
Headache
Dizziness
Lower abdominal pain
Menstrual irregularity / bleeding not related to menses / delayed menses
Breast tenderness
Fatigue

Interactions

Enzyme-inducing drugs (e.g. used within the last 4 weeks) may reduce efficacy - use a Cu-IUD or take a double dose as above (eMC 4.2/4.4; full 4.5 text not in source)

Clinical monograph

How it works

Levonorgestrel mimics progesterone, principally inhibiting or delaying ovulation and thickening cervical mucus; in intrauterine use it also produces local endometrial suppression.

Prescribing in practice

As emergency contraception it is more effective the sooner it is taken after unprotected intercourse and works mainly by delaying ovulation, so it is ineffective once ovulation has occurred and does not disrupt an established pregnancy.
Efficacy of oral emergency contraception may be reduced by enzyme-inducing drugs and in women of higher body weight, where an alternative such as a copper intrauterine device should be considered.
Vomiting shortly after an oral dose may require a repeat dose, and irregular bleeding can follow use.

Monitoring

No routine laboratory monitoring is needed; advise a pregnancy test if the next period is delayed and review contraceptive plans.

Counselling the patient

Take emergency contraception as soon as possible after unprotected sex for best effect.
Seek advice and take a pregnancy test if your period is more than a few days late.
This does not protect against future episodes or against sexually transmitted infections.

Evidence & guidelines

WHO and NICE-aligned guidance support levonorgestrel for emergency contraception, noting reduced efficacy compared with a copper intrauterine device and after ovulation has occurred.

Reference: FSRH Emergency Contraception; FSRH Intrauterine Contraception; UKMEC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways