Ethambutol — what it does and what to watch for

Ethambutol is an antibiotic used as part of combination therapy for tuberculosis (TB). It helps stop TB bacteria from growing, but it’s never used alone because resistance can develop quickly. If you’re prescribed ethambutol, this page gives clear, practical tips on how to take it and the safety checks you should expect.

How to take ethambutol

Doctors dose ethambutol by weight. Adults usually get around 15–25 mg per kg of body weight once daily. Your provider will pick an exact dose and schedule based on your weight, other TB drugs, and kidney function. Always follow the prescription—don’t skip doses and don’t stop early, even if you feel better. Stopping a TB drug too soon raises the chance the bacteria will become resistant.

Take ethambutol with or without food, as your doctor advises. Keep a consistent routine so you don’t miss doses. If you forget one, check with your prescriber or pharmacist for the best next step—don’t double up unless told to.

Side effects and vision monitoring

The most important side effect is optic neuropathy — damage to the optic nerve. That can cause blurred vision, trouble seeing colors (especially red vs. green), or a drop in visual sharpness. These changes may be reversible if ethambutol is stopped early, so quick action matters.

Your clinician should test your vision before starting ethambutol and then regularly while you’re on it. Common checks include visual acuity and color vision tests. If you notice any change in sight, contact your healthcare provider immediately and stop the medication only if your doctor tells you to.

Other common side effects include nausea, headache, dizziness, joint pain, or rash. Most are mild, but any new, worrying symptom deserves a call to your provider.

Ethambutol is cleared by the kidneys. If you have reduced kidney function, your doctor may lower the dose or space it out. Be sure to tell your provider about all medicines, supplements, and herbal products you take. They’ll check for interactions and decide what’s safe to use during TB treatment.

If you’re pregnant, breastfeeding, or planning pregnancy, talk to your clinician. TB treatment is important for both mother and baby, but the care team will weigh risks and benefits and choose the safest plan.

Store ethambutol at room temperature away from moisture and heat. Keep it out of reach of children. If you run out or lose your pills, contact your clinic—don’t try to stretch or share doses.

Need help with cost or access? Many clinics offer support programs or can point you to reliable pharmacies. Avoid buying prescription TB drugs from unknown online sellers without a valid prescription and a trustworthy pharmacy verification.

Questions about your dose, vision checks, or side effects? Ask your prescriber or pharmacist. Quick communication is the best way to keep treatment on track and protect your eyesight.