Azithromycin Side Effects: Onset, Duration & Management
Understand the potential side effects of azithromycin tablets, when they typically begin, how long they last, and when to seek medical help.
Key Takeaways
- Most common: Diarrhoea (12%), nausea (5%), abdominal pain (5%)
- Onset: GI effects within 24h; allergic reactions within 1h
- Duration: Typically 24-48h after last dose
- Serious effects: QT prolongation, liver problems, severe skin reactions
- Management: Take with food for GI upset, avoid QT-prolonging drugs
This guide provides comprehensive information about azithromycin side effects based on UK-approved safety information.
Common Side Effects of Azithromycin
| Side Effect | Frequency | Typical Experience |
|---|---|---|
| Diarrhoea | Very common (12%) | Mild, resolves with continued use |
| Nausea | Common (5%) | Worse on empty stomach |
| Abdominal pain | Common (5%) | Cramping or discomfort |
| Headache | Common (3%) | Usually mild |
| Skin rash | Uncommon (1%) | Itchy, may indicate allergy |
Note: Up to 20% of patients experience at least one side effect, but most are mild and temporary.
When Do Azithromycin Side Effects Start?
Within 1 Hour
- Allergic reactions (rash, swelling)
- Anaphylaxis (rare but life-threatening)
6-24 Hours
- Gastrointestinal effects (nausea, diarrhoea)
- Headache
Days 2-5
- Liver enzyme elevations
- QT prolongation (heart rhythm changes)
- Delayed skin reactions
- Difficulty breathing/swelling (allergy)
- Severe dizziness/fainting (heart rhythm issues)
- Bloody diarrhoea (C. difficile infection)
How Long Do Azithromycin Side Effects Last?
| Side Effect | Typical Duration | Persistent Cases |
|---|---|---|
| Gastrointestinal | 24-48h after last dose | Rarely >3 days |
| Skin reactions | 3-7 days | May require treatment |
| QT prolongation | 48-72h post-dose | Monitor if pre-existing heart condition |
| Liver enzyme changes | 1-2 weeks | Requires monitoring if severe |
Clinical insight: Azithromycin's 68-hour half-life means side effects may persist longer than with other antibiotics, but typically resolve within days.
Serious Side Effects Requiring Medical Attention
Cardiac Effects
- QT prolongation (shown on ECG)
- Torsades de pointes (life-threatening arrhythmia)
- Symptoms: Palpitations, dizziness, fainting
Hepatotoxicity
- Elevated liver enzymes (2% of patients)
- Clinical hepatitis (rare)
- Symptoms: Jaundice, dark urine, abdominal pain
Severe Skin Reactions
- Stevens-Johnson syndrome
- Toxic epidermal necrolysis
- Symptoms: Blistering, skin peeling, fever
Risk factors for serious effects: Pre-existing heart disease, concurrent QT-prolonging drugs, liver impairment, elderly patients.
Managing Azithromycin Side Effects
For Gastrointestinal Effects
- Take with small amounts of food (despite absorption reduction)
- Stay hydrated - small frequent sips of water
- Probiotics may help prevent antibiotic-associated diarrhoea
- Avoid anti-diarrhoeals unless prescribed
For Other Side Effects
| Side Effect | Management |
|---|---|
| Headache | Paracetamol (avoid NSAIDs if GI upset) |
| Mild rash | Antihistamines, stop medication if spreading |
| Oral thrush | Topical antifungals (nystatin/miconazole) |
| Photosensitivity | Sun protection, avoid UV exposure |
Frequently Asked Questions
Can azithromycin cause long-term side effects?
Most side effects resolve after stopping treatment. Rare exceptions include prolonged QT interval in susceptible individuals or antibiotic-associated colitis requiring treatment.
Why do I still have diarrhoea a week after finishing azithromycin?
This may indicate C. difficile infection. Contact your GP if diarrhoea persists >48h post-treatment, contains blood/mucus, or is accompanied by fever.
Are azithromycin side effects worse than amoxicillin?
Azithromycin causes more GI upset but fewer allergic reactions than penicillins. Cardiac risks are unique to azithromycin among common antibiotics.
Can I drink alcohol while taking azithromycin?
Moderate alcohol is unlikely to interact but may worsen nausea. Heavy drinking should be avoided due to additive liver stress.
How can I report suspected side effects in the UK?
Use the MHRA Yellow Card Scheme. Reporting helps improve drug safety monitoring.
Need Antibiotic Treatment?
If you're experiencing symptoms of a bacterial infection, our UK-registered doctors can help determine if Azithromycin Tablets is appropriate for your condition through a confidential online consultation.
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Medical Content Manager
Nabeel is a co-founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Feroz is a GMC-registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co-founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 03 November 2025
Next Review: 05 May 2026
Published on: 03 November 2025
Last Updated: 04 November 2025
