Azithromycin Dosage Guide: What You Need to Know

If you’ve been prescribed azithromycin (brand name Zithromax), the first question is usually "how much should I take?" The answer depends on what you’re treating, your age, and sometimes your weight. Below you’ll find the most common dosing schedules explained in plain language, plus a few tips to make the medicine work best for you.

Standard Adult Dosing

For most adult infections – like bronchitis, sinusitis, or skin infections – doctors use one of two simple plans:

5‑day regimen: 500 mg on day 1, then 250 mg once daily on days 2‑5.
3‑day regimen: 500 mg once daily for three straight days.

Both schedules give the same total amount of drug; the 5‑day plan spreads it out a bit more, which some people find easier on the stomach.

For sexually transmitted infections such as chlamydia, the recommendation is a single 1 g (1000 mg) dose. You take the whole tablet or the whole pack of chew‑able tablets at once, no follow‑up doses needed.

Kids and Special Situations

Children’s doses are calculated by weight. The usual rule is:

Day 1: 10 mg per kilogram of body weight.
Days 2‑5: 5 mg per kilogram each day.

So a 20‑kg child would get 200 mg on the first day, then 100 mg daily for the next four days. The medicine comes in a liquid form that makes measuring easy – just use the supplied syringe or a proper measuring spoon.

For certain lung infections like community‑acquired pneumonia, the dose may be higher: 500 mg once daily for three days, even in adults. Your doctor will tell you if you fall into that category.

How to Take It Right

Azithromycin can be taken with or without food, but a small snack can reduce stomach upset if that’s an issue for you. If you miss a dose, take it as soon as you remember, unless it’s almost time for the next one – then just skip the missed dose. Don’t double up.

Finish the full course, even if you feel better after a couple of days. Stopping early can let the infection bounce back and may encourage resistance.

Safety Tips and Common Side Effects

Most people tolerate azithromycin well. The usual side effects are mild stomach pain, diarrhea, or a slight headache. If you notice a rash, trouble breathing, or swelling of the face, call a doctor right away – those could be signs of a serious allergic reaction.

Azithromycin can interact with a few other drugs, especially those that affect heart rhythm (like certain anti‑arrhythmics) or some antacids that contain aluminum or magnesium. Let your pharmacist know about every medication you’re taking.

Quick Reference Table

Condition	Adult Dose	Child Dose (kg)
Typical bacterial infection	500 mg day 1, then 250 mg daily × 4	10 mg/kg day 1, then 5 mg/kg daily × 4
Chlamydia (STI)	1 g single dose	Same weight‑based schedule
Pneumonia	500 mg daily × 3	Weight‑based, usually 10 mg/kg day 1 then 5 mg/kg daily × 2

Keep this table handy the next time you pick up a prescription – it’s a quick way to double‑check you’re on the right schedule.

In short, azithromycin is easy to use once you know the pattern that fits your situation. Follow the dosing guide, take the full course, and watch out for any unusual symptoms. If anything feels off, give your doctor a call. Staying informed makes the treatment smoother and gets you back to feeling good faster.