Lamivudine Dosing: What You Need to Know About Dosage, Uses, and Safety

When you're managing lamivudine, a nucleoside reverse transcriptase inhibitor used to treat HIV and chronic hepatitis B. Also known as 3TC, it's one of the most commonly prescribed antiviral drugs in the world. It doesn't cure these infections, but it stops the virus from multiplying, which helps your immune system stay stronger longer. Getting the dose right matters—too little won't control the virus, and too much increases your risk of side effects without added benefit.

Lamivudine dosing changes based on what you're treating. For HIV, a chronic viral infection that attacks the body’s immune system, adults usually take 300 mg once daily, often combined with other antiretrovirals like tenofovir or efavirenz. For chronic hepatitis B, a liver infection caused by the hepatitis B virus that can lead to scarring and cancer, the standard dose is 100 mg once daily. Kids get weight-based doses, and people with kidney problems need lower amounts. Always follow your doctor’s instructions—never switch doses on your own, even if you feel fine.

What makes lamivudine tricky is resistance. If you miss doses or stop taking it, the virus can mutate and become immune to it. That’s why it’s almost always used in combo therapy, never alone. It’s also why some people on long-term treatment switch to newer drugs with higher resistance barriers. Still, for many, lamivudine remains a safe, affordable cornerstone of treatment. Side effects like headaches, nausea, or fatigue are common at first but usually fade. Serious issues like liver swelling or lactic acidosis are rare but need immediate attention.

You’ll find posts here that dig into how lamivudine fits into real-world treatment plans, how it compares to other antivirals like tenofovir, and what to watch for when combining it with other meds. Some articles cover how it’s used in pregnant women, how it affects liver health over time, and what happens if you accidentally skip a dose. There’s also practical advice on sticking to your regimen, managing side effects, and knowing when to call your doctor. Whether you’re newly diagnosed or have been on lamivudine for years, the information below is meant to help you understand not just the dose—but how to use it wisely.