Glenmark Therapeutics Emergency Contraceptive Tablet, Levonorgestrel 1.5mg, Reduces Chance of Pregnancy After Unprotected Sex Levonorgestrel 1.5mg tablets is an emergency contraceptive that can help prevent pregnancy when taken within 72 hours (3 days) of unprotected sex. The sooner you take it, the better it works. Levonorgestrel 1.5mg should not be used as regular birth control. Use as directed.