Headache After Morning-After Pill
Headache is a common and expected side effect after taking emergency contraception (morning-after pill), occurring in approximately 19% of users with both levonorgestrel and ulipristal acetate formulations, and can be managed with standard over-the-counter analgesics.
How Common Is This Side Effect?
Headache is one of the most frequently reported adverse effects of emergency contraceptive pills:
- Levonorgestrel (Plan B): Headache occurs in approximately 19% of users 1
- Ulipristal acetate: Similar headache rates (~19%) have been documented 2, 3
- This makes headache one of the top 3-5 most common side effects alongside nausea, abdominal pain, breast tenderness, and fatigue 4
The evidence from a comprehensive systematic review and meta-analysis confirms that most adverse reactions with levonorgestrel emergency contraception are common but not serious 4.
Clinical Significance and Reassurance
The headache is benign and self-limited. According to FDA labeling, headache is listed as an expected side effect that does not require discontinuation or medical intervention 1. The systematic review of levonorgestrel safety data identified headache as a common, non-serious adverse event 4.
Management Approach
Immediate Management:
- Over-the-counter analgesics are appropriate for symptomatic relief
- Standard doses of NSAIDs (ibuprofen 400-800 mg) or acetaminophen with aspirin and caffeine combinations can be used 5
- No specific contraindications exist for treating this headache with standard analgesics
When to Seek Further Evaluation:
The headache from emergency contraception should be distinguished from more serious headache presentations. You should consider further evaluation if:
- Headache is severe, sudden-onset, or "worst headache of life"
- Associated with neurological symptoms (vision changes, weakness, confusion)
- Persistent beyond several days
- Associated with severe abdominal pain (which could indicate ectopic pregnancy if the emergency contraception fails) 1
Important Caveats
Do not confuse this with contraindications: The FDA labeling clearly states that allergy to levonorgestrel is a contraindication, but headache itself is not 1. Women with pre-existing migraine conditions can still use emergency contraception, though they should be aware headache may occur.
Timing considerations: The headache typically occurs within hours to days after taking the pill and resolves spontaneously. If headache persists beyond one week or worsens, consider alternative diagnoses.
No dose adjustment needed: Unlike nausea/vomiting (which may require redosing if vomiting occurs within 2-3 hours), headache does not affect the efficacy of emergency contraception and requires no special dosing considerations 1.
Comparison Between Formulations
Both levonorgestrel and ulipristal acetate have similar headache rates (~19%), so switching formulations to avoid headache is not indicated 2, 3. The choice between these agents should be based on timing after intercourse and efficacy considerations rather than side effect profiles.