Pharmaceutical19-nortestosteroneProgestogenOralIntrauterine

Levonorgestrel

Also known as LNG · Plan B · Mirena (IUS) · Levonelle

Written by enwyReviewed 5 Aug 20261 sources0 comments

A potent second-generation 19-nortestosterone progestin, the active enantiomer of norgestrel. Backbone of many combined pills, progestin-only pills, hormonal IUDs and emergency contraception. Comparatively low VTE risk among combined-pill progestins.

01 Overview

Levonorgestrel is among the most-used progestins worldwide, appearing in combined oral contraceptives, the progestin-only 'mini-pill', levonorgestrel-releasing intrauterine systems (Mirena/Kyleena), and single-dose emergency contraception. It is potent and androgenic relative to newer progestins.

Among combined-pill progestins, levonorgestrel is associated with lower venous thromboembolism risk than desogestrel, gestodene or drospirenone, making it a common first-line choice. Its androgenicity can worsen acne in some users.

02 Mechanism

Progesterone-receptor agonist with androgenic activity; thickens cervical mucus, suppresses ovulation (higher doses) and thins/stabilises endometrium. Emergency use mainly delays ovulation.

03 Dosing

Tier	Dose	Route	Notes
Progestin-only pill	0.03 mg/day	Oral	30 mcg daily continuous.
Emergency contraception	1.5 mg	Oral	Single 1.5 mg dose ASAP within 72 h.

04 Effects

Effect	Magnitude	Evidence
ContraceptionHighly effective across pill, IUS and emergency formats.		Clinical
Reduced menstrual bleeding (IUS)LNG-IUS markedly reduces heavy menstrual bleeding.		Clinical

05 Side effects

Effect	Severity	Frequency	Evidence	Countermeasures
Irregular bleedingSpotting and unpredictable bleeding, especially with IUS and POP.	Mild	Very common	Clinical
AcneAndrogenic progestin can worsen acne in susceptible users.	Mild	Common	Clinical

06 Legal status

United States

Rx / OTC (emergency contraception OTC)

as of Jan 2026

United Kingdom

POM / P (EC pharmacy)

as of Jan 2026

07 References

Venous thrombosis risk of oral contraceptives by progestogen typeBMJ, 2011

08 Discussion0 comments

Create account

Discussion is moderated. No sourcing, vendor names or price talk — those comments are removed, and repeat posts are banned.

This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.