What are the side effects of Abacavir?
Last updated September 6, 2026.
**Abacavir can cause nausea, headache, tiredness, vomiting, and sleep problems, as well as a serious allergic reaction.** Before you start, your clinician should check for HLA-B*5701, a genetic marker linked to higher allergy risk; a negative result does not eliminate that risk. Call your prescriber immediately if you develop symptoms from two or more allergy groups: fever; rash; digestive symptoms; marked tiredness or aches; and respiratory symptoms. Other serious effects include liver problems and lactic acidosis, a buildup of acid in your blood. Keep your medication Warning Card with you and discuss persistent side effects before changing your dose.
What to do
- **Check screening:** Confirm your HLA-B*5701 result with your prescriber before starting abacavir.
- **Carry your Warning Card:** Use the symptom groups on your card to recognize when you need immediate medical advice.
- **Report persistent symptoms:** Tell your clinician if nausea, headaches, or sleep problems persist or disrupt your day.
- **Restart only with guidance:** Contact your prescriber before restarting after an interruption, and never restart after an allergic reaction.
- **Review heart health:** Discuss your heart disease risk with your clinician because abacavir may increase heart attack risk.
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