Ethambutol: what it treats and how to stay safe

Ethambutol is a medicine used as part of combination therapy for tuberculosis (TB). It helps stop the TB bacteria from growing while other drugs kill them. Doctors usually give ethambutol along with at least two other TB medicines to prevent resistance.

Before you start ethambutol, know that the drug is prescription-only and should be used under medical supervision. If you buy medicines online, stick to licensed pharmacies and keep your treatment linked to a doctor so tests and dose changes happen on time.

Common side effects and the big one: vision changes

Most people tolerate ethambutol well, but side effects can occur. The most important is optic neuropathy — a problem with the optic nerve that causes blurred vision, reduced sharpness, or trouble seeing reds and greens. This is dose-related and becomes more likely at higher doses or in people with kidney problems.

Other side effects include mild stomach upset, headache, and, rarely, peripheral nerve symptoms like numbness or tingling. If you notice any new vision trouble, stop the drug and contact your prescriber immediately. Stopping early often leads to recovery; leaving the drug on can cause longer-lasting damage.

Practical tips: dosing, monitoring, and everyday care

Typical ethambutol dosing is based on body weight; doctors tailor the exact dose and adjust for kidney function. Don’t try to adjust the dose yourself. Your care team should order a baseline eye check — visual acuity and color testing — and repeat checks during treatment, often monthly while you're taking the drug.

Simple daily steps help catch problems early. Test your vision quickly if things seem off: notice blurriness, faded colors, or trouble reading. Ask someone close to you if they see changes in how your eyes react to light or color. Keep a record of any symptoms and the dates you first noticed them — that helps your provider decide quickly.

Take ethambutol with or without food. If stomach upset bothers you, take it with a meal. Store tablets at room temperature, away from moisture and children. If you have kidney disease, diabetes, or are older, tell your care team — they may monitor you more closely or change the dose.

Ethambutol works best as part of a full TB plan. Don’t stop treatment early and always follow your prescriber’s instructions for tests and follow-ups. If you have questions about interactions, pregnancy, or buying medicine online, talk to a pharmacist or doctor who knows your full medical history.