Doxycycline: what it treats, how to use it, and safety tips

Doxycycline is a common antibiotic that treats very different problems — from acne to Lyme disease to malaria prevention. That makes it handy, but it also means you should know the right dose, how to avoid side effects, and when not to take it.

When people take doxycycline

Doctors prescribe doxycycline for respiratory infections, acne, certain STIs (like chlamydia), Lyme disease, Rocky Mountain spotted fever, and as malaria prevention for some trips. It’s also used for long-term acne control at lower doses. The exact dose and length depend on the problem — don’t guess.

Practical dosing and how to take it

Typical adult dosing is 100 mg twice daily for many infections. For malaria prevention it’s usually 100 mg once daily starting 1–2 days before travel and continuing 4 weeks after returning. For uncomplicated chlamydia the common regimen is 100 mg twice daily for 7 days. For acne, doctors may use 50–100 mg once daily for weeks to months.

Take doxycycline with a full glass of water and stay upright for 30 minutes. That lowers the chance of irritating or damaging the esophagus. If it upsets your stomach, take it with food — but avoid calcium-rich meals, milk, antacids, or iron supplements within 2–3 hours of a dose; those reduce absorption.

Use sunscreen and wear protective clothing. Doxycycline can cause strong sun sensitivity — you can get bad sunburns quickly.

Avoid doxycycline in pregnancy and in children under 8 years old because it can affect fetal development and tooth growth. If you’re pregnant or breastfeeding, ask your clinician for alternatives.

Watch for key drug interactions: warfarin (may boost bleeding risk), certain antacids/iron supplements (reduce effectiveness), and isotretinoin (rare risk of raised intracranial pressure). There’s weak evidence it lowers oral contraceptive effectiveness — use backup contraception if you’re worried.

Common side effects are nausea, diarrhea, yeast infections, and photosensitivity. Serious but rare issues include severe allergic reactions and liver problems. If you get severe abdominal pain, jaundice, or trouble breathing, seek medical care immediately.

Antibiotic resistance matters. Only take doxycycline when a clinician prescribes it for a diagnosed or strongly suspected infection. Finish the full course unless your doctor tells you otherwise.

Buying tips: get doxycycline from a licensed pharmacy and expect a prescription. Be cautious with online sellers that don’t ask for one. Check packaging, expiry date, and the pharmacy’s credentials. If pills look different than described or packaging is damaged, don’t use them.

Questions for your prescriber: Why am I getting doxycycline? What dose and length do you recommend? Any interactions with my other meds? What signs should make me stop the drug? These three quick questions help prevent problems and keep treatment on track.