Doxycycline Dose for Adults: What to Take and for How Long

The standard doxycycline dose for adults is 200 mg on first day (taken as 100 mg every 12 hours), followed by 100 mg once daily as a maintenance dose. For more severe infections, maintenance dose stays at 100 mg twice a day for full course of treatment.

That said, your exact dose depends on what condition being treated and how your body responds. Doxycycline is a broad spectrum tetracycline antibiotic used for everything from respiratory and skin infections to sexually transmitted infections and malaria prevention. So

What Is Dose for Common Infections?

For most bacterial infections in adults, including respiratory infections, skin infections, and urinary tract infections, pattern is same. You start with a loading dose of 200 mg on first day, then drop to 100 mg once a day after that. Your doctor may keep dose at 100 mg twice a day if infection is more serious or stubborn.

Most courses run 7 to 10 days for things like pneumonia, bronchitis, or sinus infections. For skin infections like cellulitis, some people may need to stay on it a bit longer, up to 14 days, depending on how quickly symptoms improve. The important thing is to finish full course, even if you start feeling better before medication runs out. Stopping early can allow bacteria to come back and potentially become resistant to antibiotic.

What Is Dose for Sexually Transmitted Infections?

Doxycycline is one of most commonly prescribed antibiotics for treating bacterial STIs. specific dosing depends on infection being treated.

For chlamydia, standard dose 100 mg twice a day for 7 days. This is one of most straightforward and effective treatments for uncomplicated chlamydia infections.

For syphilis, treatment is longer. Early stage syphilis in adults who cannot take penicillin is treated with 100 mg twice a day for 14 days. If syphilis has been present for more than a year, course extends to 4 weeks at same dose.

For gonorrhea, a single day regimen may be used, typically 300 mg taken as a first dose followed by another 300 mg one hour later. However, gonorrhea treatment usually involves doxycycline combined with another antibiotic like ceftriaxone.

The CDC has also recommended doxycycline as a post exposure prophylaxis (Doxy PEP) for preventing bacterial STIs in certain high risk populations. In that case, a single 200 mg dose is taken within 72 hours after unprotected sex, with a maximum of 200 mg every 24 hours.

[IMG:https://assets.getbeyondhealth.com/health-lib/blogs/manual_upload_20260216035132_doxycycline-dosing.png]

What About Acne and Rosacea?

For moderate to severe acne, doxycycline often prescribed at 100 mg once or twice daily, depending on how skin responds. Treatment courses for acne tend to be longer than for infections, sometimes lasting several weeks to a few months. Your dermatologist will work with you to find lowest effective dose and will usually taper off once your skin clears up.

For rosacea, a lower dose used. The typical prescription is a 40 mg delayed release capsule taken once daily. At this dose, doxycycline works more as an anti inflammatory agent rather than an antibiotic. It helps reduce redness and bumps associated with rosacea without contributing to antibiotic resistance.

What Is Dose for Malaria Prevention?

If you are traveling to an area where malaria is a risk, doxycycline can be used as a preventive medication. The dose for adults 100 mg once a day. You start taking it 1 to 2 days before entering malaria risk area, continue daily throughout your trip, and keep taking it for 4 weeks after you leave. The total course should not exceed 4 months.

What About Tick Borne Infections?

Doxycycline is first line treatment for Lyme disease and other tick borne illnesses like Rocky Mountain spotted fever. For Lyme disease, typical adult dose 100 mg twice a day for 10 to 21 days, depending on stage of infection. For Rocky Mountain spotted fever, treatment started immediately based on clinical suspicion and usually continues for at least 3 days after fever resolves.

How Should You Take Doxycycline?

How you take doxycycline matters just as much as how much you take. There are a few practical tips that can make a big difference in how well medication works and how you feel while on it.

First, take each dose with a full glass of water. This helps prevent one of more uncomfortable side effects, which throat irritation or esophageal ulcers. After taking your dose, stay upright for at least 30 minutes. Do not lie down right after swallowing it.

Most forms of doxycycline can be taken with food or milk to reduce stomach upset. However, some specific formulations need to be taken on an empty stomach. Check with your pharmacist about exact form you have been prescribed.

One thing to be aware of that dairy products, antacids, iron supplements, and calcium fortified foods can interfere with how well your body absorbs doxycycline. It best to space these out by at least 2 hours before or after your dose.

What Side Effects Should You Watch For?

Doxycycline is generally well tolerated. The most common side effects include nausea, stomach upset, and diarrhea. These tend to improve as your body adjusts.

One side effect that catches many people off guard is sun sensitivity. While you are on doxycycline, your skin can burn much more easily than normal, even after brief sun exposure. Wear sunscreen with at least SPF 50, cover up with hats and long sleeves, and avoid tanning beds. This sensitivity can continue for a short time after you stop taking it as well.

In women, doxycycline may increase risk of vaginal yeast infections, especially toward end of a course or after finishing it. Taking a probiotic during and after treatment may help reduce that risk.

Rare but more serious side effects include severe headaches or vision changes, which could be a sign of increased pressure in brain. If you experience these, contact your doctor right away.

When Should You Talk to Your Doctor?

Reach out to your doctor if your symptoms are not improving after 48 to 72 hours on doxycycline, or if they are getting worse. Also let your provider know if you develop watery or bloody diarrhea during or after your course, as this could point to a C. difficile infection, which needs separate treatment.

It also important to mention if you are pregnant, breastfeeding, or taking blood thinners, seizure medications, or hormonal birth control, as doxycycline can interact with these. Your doctor can help you navigate safest approach.