Important: Amoxicillin dosing is always individualized. This guide is for educational purposes only and does not replace your doctor’s instructions.
Amoxicillin is one of the most familiar names in modern medicine. Since its introduction in the 1970s, it has become a cornerstone antibiotic, prescribed to millions of patients every year. It is valued for its broad activity against bacteria, safety profile, and flexibility in dosing, which makes it suitable for both adults and children. From a sore throat in a child to a dental infection in an adult, amoxicillin is often the first prescription a doctor will consider.
Yet, despite its widespread use, many patients and caregivers have questions that go beyond the prescription slip. What exactly is the difference between the 500 mg tablet and 875 mg tablet? Why are there two different liquid suspensions (250/5 and 400/5), and how do parents know which one to use for their child? How quickly should symptoms improve, and what should you do if you accidentally miss a dose? These are the kinds of practical questions that matter in everyday life but are often left unanswered during a short doctor’s visit.
This guide brings together all of those essentials in one place. It explains the forms and strengths of amoxicillin available, how timing affects its effectiveness, and what caregivers need to know about liquid suspensions for children. It also addresses common real‑world dilemmas, like missed doses and storage questions, and gives clear advice on when it’s time to check back with your healthcare provider.
Important: Amoxicillin dosing is always individualized. The information here is educational only. Your doctor or pharmacist provides the instructions that apply to you or your child. Never change a dose or schedule without medical guidance.
Adult strengths schedules
Amoxicillin for adults is most often prescribed in tablet or capsule form, making it easy to take at home without the need for injections or hospital visits. The two strengths that patients see most frequently are 500 mg and 875 mg. There are also 250 mg tablets, but these are used less commonly in adults today and are largely considered a legacy strength, more relevant to older prescribing habits or in special circumstances.
The numbers on the box — 250, 500, 875 — refer to the amount of active antibiotic in each tablet. A 250 mg tablet contains 250 milligrams of amoxicillin, while a 500 mg tablet contains 500 milligrams, and an 875 mg tablet contains 875 milligrams. This is not just a matter of “strong” versus “weak.” The difference also relates to how often the tablets are taken during the day. Smaller doses (500 mg) are often prescribed more frequently, such as three times a day, while larger doses (875 mg) are usually taken less often, such as twice daily. Both strategies aim to maintain steady levels of the antibiotic in the bloodstream, which is crucial for killing bacteria effectively.
A frequent question patients ask is: “Is 875 mg stronger than 500 mg?” In terms of the single tablet, yes, as it contains more of the active substance. But in practice, the total daily amount of amoxicillin can be similar whether you take 500 mg three times daily or 875 mg twice daily. The difference often comes down to convenience, adherence, and how well a patient tolerates the schedule. For many adults, remembering two larger tablets per day is easier than three smaller ones. On the other hand, some people may find that smaller, more frequent doses are gentler on their stomach.
Doctors also consider factors such as severity of infection, patient weight, and other medical conditions when choosing between strengths. For example, in routine cases where compliance is a concern, an 875 mg twice‑daily regimen may be preferred because it simplifies the schedule. In situations where maintaining tighter control of blood levels is important, 500 mg three times a day may be chosen.
To put this into perspective, here’s how the most common adult tablets compare:
| Tablet strength | How it’s usually taken | Notes |
|---|---|---|
| 250 mg | Less common today | Older formulations |
| 500 mg | More frequent (e.g., 3× daily) | Most widely recognized dose |
| 875 mg | Less frequent (e.g., 2× daily) | Convenience factor |
Smaller doses taken more often and larger doses taken less frequently both aim to keep amoxicillin levels steady in the bloodstream. It’s important to note that the actual schedule and duration are individualized by the prescriber based on the type and severity of infection. The information here simply illustrates how the strengths differ in format, not in the final choice of regimen. See how amoxicillin is structured into tablets and suspensions in our guide to dosing and forms.
How long does it take to work?
One of the most common questions patients ask after starting antibiotics is: “How quickly will I feel better?” With amoxicillin, the answer depends on whether we are talking about symptom relief or bacterial clearance.
For many bacterial infections, patients often notice some improvement within 24-48 hours. Fever may start to come down, sore throats may ease, or pressure from a sinus infection may lessen. This early relief is a good sign that the antibiotic is beginning to work, but it does not mean the infection is gone. Behind the scenes, amoxicillin is targeting bacteria as they divide, disrupting their cell walls and causing them to die. This microbiological process takes time. Even after you start feeling better, some bacteria may still remain. If the antibiotic course is stopped too early, those surviving bacteria can multiply again, and in some cases develop resistance.
That is why doctors prescribe amoxicillin for a specific duration, usually five to ten days, depending on the infection. Even if you feel well halfway through, finishing the prescribed course ensures that the bacteria are completely eradicated.
It’s also worth remembering that not all infections respond equally quickly. A mild throat infection may improve rapidly, while a more complicated chest or urinary tract infection might take longer before noticeable changes occur.
In summary: symptoms may improve within 1-2 days, but the antibiotic continues working in the background for the full course. Following your doctor’s instructions and not stopping the treatment too early is essential for a lasting recovery.
Pediatric liquids (250/5, 400/5): weight‑based logic + caregiver tips
For children, amoxicillin is usually prescribed as a liquid amoxicillin suspensions rather than tablets. These suspensions come in different concentrations, most often 250 mg/5 ml and 400 mg/5 ml. The numbers show how much drug is in each teaspoon (5 ml).
To make sense of this:
250 mg/5 ml = 50 mg per ml
400 mg/5 ml = 80 mg per ml
This means the 400 mg/5 ml suspension is more concentrated. A child who needs a certain dose in milligrams will therefore take a smaller volume of the 400/5 suspension compared to the 250/5.
Weight‑based logic
Doctors calculate pediatric antibiotic doses according to the child’s weight in kilograms (kg). This ensures each child receives the right amount for their body size. For example, if a 20‑kg child needs 500 mg of amoxicillin, that equals:
- 10 ml of the 250/5 suspension (since 5 ml = 250 mg), or
- 6.3 ml of the 400/5 suspension (since 5 ml = 400 mg).
This is why you’ll often see different volumes prescribed depending on which suspension is dispensed by the pharmacy.
Illustrative pediatric chart (educational example only)
| Weight (kg) | Example dose (mg) | 250 mg/5 ml → volume | 400 mg/5 ml → volume |
|---|---|---|---|
| 5 kg | 125 mg | 2.5 ml | 1.6 ml |
| 10 kg | 250 mg | 5 ml | 3.1 ml |
| 20 kg | 500 mg | 10 ml | 6.3 ml |
| 30 kg | 750 mg | 15 ml | 9.4 ml |
| 40 kg | 1000 mg | 20 ml | 12.5 ml |
Note: These numbers are simplified to illustrate how different suspensions correspond to volumes. Real pediatric prescriptions are always individualized.
Caregiver tips
- Shake the bottle well before each dose to ensure the medicine is evenly mixed.
- Use the measuring syringe or spoon provided, not kitchen teaspoons, which are inaccurate.
- Refrigeration may be needed: some amoxicillin suspensions need to be refrigerated after reconstitution (the pharmacist adds water). Always follow the pharmacy label.
- Finish the full prescribed course, even if the child feels better.
For children, doses and volumes are calculated based on weight, and careful measurement and storage ensure the antibiotic works as intended.
Practical dosing questions
Even with a clear prescription, everyday situations can raise doubts. Here’s what patients and caregivers often want to know.
What if I miss a dose? If you forget a dose, take it as soon as you remember. If the next scheduled dose is already near, skip the missed one and return to your regular rhythm. Never double up to “catch up” — this only increases the chance of side effects like nausea or diarrhea. Missing a single pill is not a catastrophe, but repeated missed doses can weaken treatment and allow bacteria to survive. If you find yourself forgetting often, consider using a pill organizer or phone reminders to stay on track.
Should I take amoxicillin with meals? It works with or without food. If you have a sensitive stomach, take it with a small meal or snack to reduce nausea.
How should I store it? Tablets and capsules: keep at room temperature, away from humidity (not in the bathroom cabinet). Liquid suspensions: once reconstituted by the pharmacist, some brands require refrigeration. They usually expire within 7-14 days, even if not finished. After that, the bottle should be discarded. For details about side effects and expiration rules, see our amoxicillin safety guide.
What if my child spits out a dose? If a child spits it out immediately, repeat the dose in full. If it’s unclear how much was swallowed, don’t guess. Call your doctor or pharmacist before re‑dosing, as giving too much is not safer than giving too little. Some caregivers find success mixing the liquid with a small amount of juice or using an oral syringe to squirt it gently along the inside of the cheek.
Why is timing important? Because amoxicillin works best when blood levels remain steady. Skipping or delaying doses can give bacteria time to recover. Aim to take it at evenly spaced intervals, whether that means every eight or every twelve hours.
When to check back with your clinician
Taking amoxicillin as prescribed usually leads to steady improvement, but there are times when it’s important to reach out to your healthcare provider rather than waiting for the course to finish.
The first is lack of improvement. If your symptoms have not begun to ease after 48-72 hours, it may mean that the bacteria are resistant, or that the illness is caused by something other than bacteria. A doctor can reassess and decide whether a different antibiotic or a completely different treatment is needed.
The second warning sign is the appearance of new or worsening symptoms. For example, a spreading skin rash, severe diarrhea, abdominal pain, or yellowing of the eyes and skin can signal complications or side effects that require attention.
Another common problem is difficulty keeping the medicine down. If vomiting or persistent diarrhea prevents doses from being absorbed, the antibiotic cannot work properly. In this situation, a switch to a different form or route (such as an injection) may be necessary. It is also sensible to call back if you realize you have been taking the medicine incorrectly, for example, missing multiple doses, misunderstanding the schedule, or storing the liquid improperly. Doctors and pharmacists would rather help you adjust than risk ineffective treatment.
Finally, patients with underlying conditions such as liver disease, kidney disease, or immune suppression should maintain closer communication during treatment, since small changes can matter more in these contexts.
The bottom line is that improvement should be visible within a few days. If it’s not or if something feels wrong, checking in with your clinician is the safest course of action.
FAQ
What is the typical time to improvement? Most people feel better in 24-48 hours, but the bacteria take longer to clear; always finish the prescribed course.
How long amoxicillin takes to work? Most people feel better in 24-48 hours, but the bacteria take longer to clear. Always finish the prescribed course.
What if I miss a dose? Take it as soon as possible unless the next dose is near. Never double up.
What’s the difference between 500 mg and 875 mg tablets? Both deliver the same antibiotic. 875 mg is simply a higher‑strength tablet usually taken less often per day.
Can I take amoxicillin on an empty stomach? Yes, it works either way. Some people take it with food to reduce nausea.
How is liquid amoxicillin measured for kids? Doctors calculate the dose by weight. Caregivers should use the provided syringe or measuring spoon, not household cutlery.
Planning to order amoxicillin online? Take a moment to go through our guide first.
References
- MedlinePlus. (2024). Amoxicillin. National Library of Medicine.
- U.S. Food and Drug Administration. (2024). Amoxicillin – Drug label information. DailyMed.
- Centers for Disease Control and Prevention. (2023). Antibiotic prescribing and use – Common illnesses. U.S. Department of Health Human Services.
- National Institute for Health and Care Excellence. (2023). Otitis media (acute): antimicrobial prescribing. NICE guideline NG91.
- Infectious Diseases Society of America. (2012). IDSA clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis. Clinical Infectious Diseases, 55(10), e86-e102.