What to Do After Unprotected Sex: Hour-by-Hour Clinical Action Plan
A clear, evidence-based triage guide for emergency contraception, STI exposure prophylaxis, and testing windows.
Clinical Review Standard
Reviewed by Dr. Rebecca Martinez, MD & Emergency Medicine Review Panel. Grounded in consensus guidelines from CDC, WHO, NHS, and ACOG.
- Hour 0–72: Take a Levonorgestrel emergency pill (Plan B, i-Pill) as soon as possible for maximum effectiveness.
- Hour 0–120 (5 Days): Ulipristal acetate (ella) or a Copper IUD insertion remains highly effective up to 120 hours post-intercourse.
- Hour 0–72 (HIV PEP): If at high risk for HIV exposure, consult a clinic or emergency department immediately for PEP.
- Day 14+: Take an at-home urine hCG pregnancy test 14 days after intercourse for early results, or at 21 days for definitive accuracy.
1. Immediate Steps (First 24 to 72 Hours)
The primary objective immediately after unprotected sex is preventing unintended pregnancy. Emergency contraceptive pills work by temporarily delaying or suppressing ovulation so that no egg is released to meet surviving sperm. Levonorgestrel (1.5mg single dose) is available over-the-counter without a prescription or age restriction in most countries and is most effective when taken in the first 24 hours.
2. Options Up to 120 Hours (5 Days)
If more than 72 hours have elapsed, Plan B efficacy declines sharply. However, Ulipristal acetate (ella)—a prescription pill—maintains consistent efficacy up to 120 hours (5 days) post-intercourse and is more effective for individuals weighing over 165 lbs (75 kg). Additionally, having a Copper IUD inserted by a clinician within 5 days is over 99.9% effective and provides 10+ years of ongoing birth control.
3. HIV Post-Exposure Prophylaxis (PEP) & STI Triage
If there is any possibility of exposure to HIV from an unknown or HIV-positive partner not on suppressive treatment, Post-Exposure Prophylaxis (PEP) must be started within 72 hours (ideally within 24 hours). PEP is a 28-day antiretroviral regimen that stops HIV from establishing infection.
Myths vs. Clinical Facts
Evidence: ACOG and the FDA confirm that emergency contraceptives have zero abortifacient properties.
Frequently Asked Questions
When should I take a pregnancy test after unprotected sex?
Hormone levels (hCG) require time to build. Take a test 14 days after the sexual encounter. A test taken 21 days after is definitive.
When to Consult a Healthcare Professional
- • Known exposure to HIV within the last 72 hours (visit emergency care for PEP immediately).
- • Severe lower abdominal pain on one side 2–4 weeks later (potential ectopic pregnancy).
- • Signs of active STI symptoms such as genital ulcers, burning urination, or fever.
- CDC — Emergency Contraceptive & Post-Exposure Guidelines
- World Health Organization (WHO) — Emergency Contraception Fact Sheet
- ACOG Practice Bulletin — Emergency Contraception
- Planned Parenthood — Emergency Contraception Guidance