Metformin Side Effects: Common and When to Call a Doctor
Metformin is often the first medicine prescribed for type 2 diabetes. Most people tolerate it well, but some notice side effects, especially at the start.
Quick answer
- The most common side effects are stomach related, such as nausea, loose stools, bloating and a metallic taste.
- These often settle with time and can be reduced by taking metformin with food or using an extended-release form.
- Rare but serious problems, such as lactic acidosis, need urgent care.
Common Side Effects
- Nausea or reduced appetite
- Loose stools or diarrhoea
- Gas and bloating
- Stomach discomfort
- A metallic taste
How to Reduce Them
- Take with or right after meals
- Start at a low dose and increase slowly, as your doctor advises
- Ask about an extended-release version
- Avoid skipping meals
Vitamin B12
Long-term use can lower vitamin B12 in some people, which may cause tingling or numbness in the feet. Your doctor may check B12 periodically.
When to Call a Doctor
- Severe or persistent vomiting or diarrhoea
- Marked weakness, fast breathing or severe muscle pain
- Unusual drowsiness or stomach pain
- Signs of dehydration
Situations Needing Caution
Kidney problems, severe infection, dehydration, heavy alcohol use and contrast dye scans may need metformin to be paused. Tell your doctor before such procedures.
Does Metformin Harm the Kidneys?
Metformin does not damage kidneys in itself, but dose adjustment or stopping may be needed if kidney function is reduced.
Key Takeaways
- Stomach upset is the most common issue.
- Taking it with food helps.
- Check B12 levels over time.
- Serious reactions are rare but need urgent care.
- Do not stop it without medical advice.
Final Thoughts
For most people the benefits of metformin outweigh the side effects. If you struggle with it, there are options. For medicine review, you can consult Dr. Tamoghna Das, an internal medicine and cardio-diabetology specialist at Medcare Diabetes & Obesity Clinic.
This article is part of our guide to diabetes medicine treatment options, written for patients and families in Bongaigaon.
FAQs
Can metformin cause weight loss?
Some people lose a small amount of weight, mainly through reduced appetite, but results vary.
How long do side effects last?
Stomach symptoms often improve within a few weeks.
Should I take metformin before or after food?
Usually with or right after meals to reduce stomach upset.
Is long-term use safe?
It has been used for many years and is generally considered safe with regular monitoring.
Can I drink alcohol on metformin?
Heavy drinking raises the risk of complications. Discuss limits with your doctor.
What if I miss a dose?
Take it with the next meal if remembered soon, but do not double the dose.
Sources
Medically reviewed by Dr. Tamoghna Das, MBBS, MD (Medicine) · Assam Council of Medical Registration No. 20276 · Last reviewed 6 October 2026
Medical disclaimer. This article is for general information only. It is not a diagnosis and is not a substitute for a consultation with a doctor. For advice about your own health, please book an appointment. Read our medical disclaimer.
Seek urgent care now, call 108 or 112, or go to the nearest emergency department if you have chest pain, sudden breathlessness, fainting, weakness on one side of the body, very high blood sugar with vomiting or drowsiness, repeated low blood sugar with confusion, or a foot wound with redness, swelling or fever.
