Can you take Plan B (levonorgestrel) during ovulation?

Can You Take Plan B During Ovulation?

Yes, you can take Plan B (levonorgestrel) during ovulation, but it may be significantly less effective during this time compared to when taken before ovulation occurs. 1, 2

How Plan B Works

Plan B (levonorgestrel 1.5 mg) works primarily by:

1. Delaying or preventing ovulation - This is its main mechanism of action 1, 3
2. Timing matters significantly - Effectiveness decreases as you get closer to ovulation 4

When taken during different phases of your cycle:

• Before ovulation: Highly effective at preventing pregnancy by delaying/inhibiting egg release 4
• During ovulation: Significantly reduced effectiveness 4, 5
• After ovulation: Limited to no effectiveness 4

Effectiveness Based on Timing

• Within 24 hours of unprotected sex: Most effective (prevents ~7 out of 8 potential pregnancies) 2
• Within 72 hours (3 days): Still effective but decreasing 2, 6
• After 72 hours: Effectiveness continues to decline 6
• After 120 hours (5 days): Risk of pregnancy increases over five times compared to taking it within 24 hours 6

Research on Ovulation Timing

Research specifically examining Plan B's effectiveness around ovulation shows:

• In women who had intercourse during fertile days and took Plan B after ovulation had already occurred, the pregnancy rate was similar to what would be expected without any contraception 4
• In women who had intercourse during fertile days but took Plan B before ovulation, no pregnancies occurred despite expectations of several 4
• When administered at the time of LH surge (right before ovulation), levonorgestrel prevented follicular rupture in only 14% of cases compared to ulipristal acetate's 79% 5

Important Considerations

• Take it anyway: Even during ovulation, taking Plan B is better than taking nothing at all 1, 2
• Take it ASAP: The sooner you take it after unprotected sex, the better it works 2, 6
• Side effects: May include changes in your period timing/flow, nausea, abdominal pain, tiredness, headache, dizziness, and breast tenderness 2
• Vomiting concern: If you vomit within 2 hours of taking Plan B, contact a healthcare provider about possibly taking another dose 2

Alternative Options

If you're concerned about Plan B's reduced effectiveness during ovulation:

• Copper IUD: Can be inserted within 5 days of unprotected sex and is more effective than hormonal emergency contraception 1
• Ulipristal acetate (ella): More effective than Plan B when taken close to or during ovulation 5

Common Pitfalls

• Mistiming your cycle: Many women incorrectly estimate their ovulation day 4
• Waiting too long: Delaying taking Plan B significantly reduces its effectiveness 2, 6
• Relying on Plan B as regular contraception: It's less effective than regular birth control methods and is intended for emergency use only 2
• Not following up: If your period is more than a week late after taking Plan B, take a pregnancy test 2

Remember that Plan B does not protect against sexually transmitted infections, and if you're having regular unprotected intercourse, you should consider a more reliable form of ongoing contraception 1.