Most amoxicillin prescriptions last between 5 and 10 days, depending on the type of infection being treated. A strep throat course runs a full 10 days, while a sinus infection or skin infection typically requires only 5 to 7 days. Your prescription length reflects what works best for your specific condition, so the most reliable answer is always the number of days your prescriber wrote on the label.
Common Courses by Infection Type
The length of an amoxicillin course varies significantly based on what it’s treating. Here are the most common durations:
- Strep throat: 10 days. This is one of the longer courses, and the CDC specifically recommends a full 10-day course for all oral antibiotics in this class when treating strep. Shorter courses of amoxicillin (or its parent drug penicillin) are less effective at clearing the bacteria from the throat, even when symptoms improve quickly.
- Sinus infections: 5 to 7 days for adults with uncomplicated cases.
- Skin infections (cellulitis): 5 to 7 days, provided symptoms are improving.
- Ear infections in children: 5 to 7 days for children aged 2 and older with mild, uncomplicated infections. Younger children or those with severe symptoms may be prescribed a longer course.
- Dental infections: 3 to 7 days at 500 mg three times daily. For dental procedures requiring preventive antibiotics, the protocol is different: a single 2-gram dose taken 30 to 60 minutes before the appointment.
- Urinary tract infections: Typically 3 to 7 days, though amoxicillin is not the first-choice antibiotic for most UTIs.
When You’ll Start Feeling Better
Most people notice improvement within 24 to 72 hours of their first dose. The timeline depends on the severity of the infection, its location, and your overall health. A mild sinus infection might feel noticeably better after a day, while a deeper skin infection could take the full three days before the swelling and redness start to recede.
Feeling better early does not mean the infection is gone. Amoxicillin works by killing bacteria during their growth cycles, and not all bacteria are actively dividing at the same time. The first wave of relief comes when enough bacteria have been killed to reduce inflammation, but pockets of surviving bacteria can regrow if you stop too soon.
Why the Full Course Matters
Stopping amoxicillin early increases the risk of two things: relapse and resistance. A relapse means the infection comes back, sometimes worse than before, because surviving bacteria repopulate. Resistance is a broader concern. When bacteria are exposed to an antibiotic but not killed off completely, the survivors are more likely to be the ones with natural defenses against that drug. Those survivors multiply, and the next time you (or someone else) need amoxicillin, it may not work as well.
The World Health Organization notes that completing the prescribed course helps reduce the speed at which bacteria develop resistance. This is especially relevant for strep throat, where incomplete treatment can lead to complications like rheumatic fever, a condition that affects the heart.
Is a Shorter Course Ever Okay?
For certain infections, yes. Medical guidelines have been moving toward shorter courses where the evidence supports them. A large meta-analysis of 50 randomized trials found that for strep throat, shorter antibiotic courses (5 days or fewer) using certain drug classes were just as effective as longer courses. But this did not hold true for penicillin-type antibiotics like amoxicillin specifically. When researchers isolated studies comparing short-course penicillin to long-course penicillin, the longer course was significantly better at clearing the bacteria.
This is why your doctor might prescribe 5 days of one antibiotic but 10 days of amoxicillin for the same condition. The duration is matched to the drug, not just the disease. If you feel your course is longer than expected, that’s the reason.
What to Do If You Miss a Dose
Take the missed dose as soon as you remember. If your next scheduled dose is coming up soon, skip the missed one and resume your normal schedule. Do not take two doses at once to make up for it. Doubling up increases the chance of side effects like diarrhea and nausea without meaningfully improving how well the antibiotic works.
If you’re consistently forgetting doses, try setting a phone alarm or tying your doses to meals. Amoxicillin can be taken with or without food, so anchoring it to breakfast, lunch, and dinner (for a three-times-daily prescription) is a simple way to stay on track. Missing one dose over a full course is unlikely to cause problems, but missing several can reduce the drug’s effectiveness.
Side Effects and Finishing the Course
The most common side effects of amoxicillin are diarrhea, nausea, and skin rash. These are generally mild and resolve once you finish the course. Interestingly, a meta-analysis found that shorter antibiotic courses actually had a slightly higher rate of reported side effects (about 18%) compared to longer courses (about 12%), possibly because shorter regimens sometimes use higher doses or more potent drug classes.
If you develop hives, facial swelling, or difficulty breathing, that signals an allergic reaction, which is different from a side effect. Stop taking the medication and get medical attention. A mild rash that appears several days into treatment is worth reporting to your prescriber but is not necessarily a reason to stop on your own. Switching to a different antibiotic mid-course is common and straightforward when side effects become intolerable.
Taking Amoxicillin Effectively
Space your doses as evenly as possible throughout the day. If you’re prescribed three doses daily, aim for roughly every 8 hours. If it’s twice daily, every 12 hours. Consistent spacing keeps the drug at a steady concentration in your bloodstream, which is how it works best. Taking all your doses bunched together in the morning and then going 16 hours without one creates gaps where bacteria can recover.
Store the liquid form (common for children) in the refrigerator, and shake it before each dose. Capsules and tablets can be stored at room temperature. If you have leftover amoxicillin from a previous prescription, don’t use it for a new infection. It may have degraded, the dose may be wrong for your current condition, and self-prescribing antibiotics contributes to resistance.