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Published on: 2/24/2026
Amoxicillin may not work if your illness is viral, the bacteria are resistant or atypical, the dose or duration is off, the infection is more severe or complicated, or the problem is not an infection. You should usually see some improvement within 48 to 72 hours; if not, or if symptoms worsen, contact your clinician, and seek urgent care for red flags like high fever, trouble breathing, chest pain, or confusion.
There are several factors to consider and specific, medically approved next steps such as culture testing, imaging, switching antibiotics, and supportive care. See the complete guidance below to choose the safest next move for your situation.
If you've been taking amoxicillin and your infection doesn't seem to be improving, you're not alone. While amoxicillin is one of the most commonly prescribed and effective antibiotics, it doesn't work for every infection — and it doesn't work in every situation.
Understanding why your body isn't responding can help you take the right next steps safely and confidently.
Amoxicillin is a penicillin-type antibiotic. It treats infections by killing certain types of bacteria. Doctors commonly prescribe it for:
It works well against many bacterial infections — but it does not work against viruses.
If your symptoms are lingering, there are several medically recognized reasons why.
This is one of the most common reasons amoxicillin doesn't work.
Antibiotics treat bacteria — not viruses.
Conditions often caused by viruses include:
If your illness is viral, amoxicillin won't help, no matter how long you take it.
Antibiotic resistance is increasing worldwide. This means some bacteria have evolved and are no longer killed by medications that used to work — including amoxicillin.
This can happen if:
Signs resistance may be involved:
Your doctor may:
Do not stop or switch antibiotics without medical advice.
Some infections are caused by bacteria that amoxicillin does not treat effectively, including:
For example, Mycoplasma lacks a cell wall — and since amoxicillin works by attacking bacterial cell walls, it won't be effective.
If you've had:
You may be dealing with an atypical infection like Mycoplasma Infection, which requires different antibiotics to treat effectively.
If an atypical infection is suspected, doctors usually prescribe a different class of antibiotics such as macrolides or doxycycline.
Sometimes the medication is correct — but:
For amoxicillin to work properly, it must stay at effective levels in your bloodstream.
Common issues include:
Even if you feel better, always finish the full course unless your doctor instructs otherwise.
Incomplete treatment increases the risk of recurrence and antibiotic resistance.
If symptoms are not improving, it could mean:
Examples include:
Red flags that require prompt medical attention:
If you experience these, seek medical care immediately.
Some conditions mimic infection but aren't caused by bacteria:
If amoxicillin hasn't helped and your symptoms persist, your doctor may need to reconsider the diagnosis.
Most people notice improvement within:
You should see some improvement by day three.
If you feel completely unchanged — or worse — contact your healthcare provider.
When amoxicillin doesn't seem to work, avoid these common mistakes:
These actions can worsen resistance and delay proper treatment.
If your infection is lingering, here's a smart plan:
Ask yourself:
Your provider may:
If respiratory symptoms are lingering, you may benefit from an online symptom check for Mycoplasma Infection before your visit. It can help guide a more focused conversation with your doctor.
While antibiotics treat bacteria, your immune system does much of the work.
Support recovery with:
While most lingering infections are manageable, seek urgent care if you develop:
These can be life-threatening and require emergency evaluation.
If amoxicillin isn't working, it doesn't automatically mean something is seriously wrong — but it does mean the situation needs reassessment.
Common reasons include:
The key is timely follow-up.
Antibiotics are powerful tools, but they are not universal cures. When used appropriately — and adjusted when needed — they remain highly effective and safe.
If your symptoms aren't improving after 72 hours, or if they worsen at any point, speak to a doctor promptly. Only a qualified healthcare professional can determine whether your infection requires a different medication, further testing, or urgent care.
Taking action early leads to better outcomes — and peace of mind.
(References)
* Bush K, Bradford PA. Mechanisms of Resistance to β-Lactam Antibiotics. Clin Microbiol Rev. 2017 Jan;30(1):1-140. doi: 10.1128/CMR.00019-16. PMID: 27881512.
* Laxminarayan R, Sridhar D, Blaser MJ, et al. Antimicrobial resistance in community-acquired bacterial infections: current evidence and treatment challenges. Lancet Infect Dis. 2021 Mar;21(3):e69-e79. doi: 10.1016/S1473-3099(20)30561-0. PMID: 33453229.
* Lykkedegn S, Gubbels S, Linstad K, Petersen G, Schønheyder HC, Christiansen CB. Antibiotic prescribing in the community after initial amoxicillin treatment failure for acute respiratory tract infection: a Danish nationwide cohort study. J Antimicrob Chemother. 2019 Apr 1;74(4):1047-1056. doi: 10.1093/jac/dky546. PMID: 30698715.
* van der Does Y, Limper M, Jie KE, et al. Biomarkers for bacterial or viral infection: what's the evidence? BMJ. 2019 May 22;365:l1726. doi: 10.1136/bmj.l1726. PMID: 31118187.
* Metlay JP, Waterer GW, Long AC, et al. IDSA Guidance on the Treatment of Community-Acquired Pneumonia in Adults: 2019 Update. Executive Summary. Clin Infect Dis. 2021 Apr 8;72(7):1108-1114. doi: 10.1093/cid/ciaa003. PMID: 33450912.
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