Doxycycline Dosage: What You Need to Know

If you’ve been prescribed doxycycline, you probably wonder how much to take and for how long. The good news is the dosing is pretty straightforward once you match the dose to the infection you’re treating. Below you’ll find the most common adult and child schedules, adjustments for special conditions, and practical tips to avoid side effects.

Typical adult dosing

For most bacterial infections, doctors start adults on 100 mg twice a day (every 12 hours). That’s the standard for acne, urinary‑tract infections, and many respiratory bugs. If you’re treating something like Lyme disease or certain STIs, the dose may stay at 100 mg twice daily for a full 2‑4 weeks. Some skin infections require a lower dose—often 50 mg twice a day—so always follow the exact prescription.

When doxycycline is given as a single daily dose, it’s usually 200 mg taken with a full glass of water in the morning. This regimen is common for malaria prophylaxis and some long‑term acne treatments. The key is to keep the dosing interval steady; skipping or doubling doses can reduce effectiveness and increase side‑effects.

Special cases and tips

Kids under 8 years old generally avoid doxycycline because it can affect tooth color. If a child older than 8 needs the drug, the dose is calculated by weight: about 2.2 mg per kilogram of body weight twice daily. For example, a 30‑kg teen would take roughly 66 mg each time, which is usually rounded to the nearest tablet strength.

Pregnant or breastfeeding women should discuss alternatives, as doxycycline can cross the placenta and appear in breast milk. If a doctor still prescribes it, the dosage may be reduced and monitored closely.

Take doxycycline with plenty of water and stay upright for at least 30 minutes. This prevents irritation or ulcers in the esophagus. Food can be eaten with the dose, but calcium‑rich products (milk, cheese) should be spaced a couple of hours apart because they can lower absorption.

If you experience nausea, a light snack or an antacid can help, but avoid taking antacids at the exact same time as the antibiotic. Common side‑effects like mild sun sensitivity mean you should wear sunscreen and a hat when you’re outdoors.

Remember to finish the full course, even if you feel better early on. Stopping early can let bacteria survive and become resistant, making future infections harder to treat.

Got questions about a specific condition or how to adjust doses for kidney problems? Talk to your pharmacist or doctor—personalized advice is the safest route.