Metformin is a biguanide used for type 2 diabetes. Immediate-release and extended-release products need their own instructions, and the exact label matters when checking strengths, age limits and tablet handling.
The approved uses and formulations described here follow US prescribing information. They may differ in other countries.
| Medicine detail | Details |
|---|---|
| Active ingredient(s) | metformin hydrochloride |
| Medicine class | Biguanide |
| Forms and strengths | Immediate-release and extended-release oral products; product-specific strengths and age labeling |
How metformin contributes
Metformin reduces liver glucose production and affects insulin sensitivity and intestinal glucose handling. It does not stimulate insulin release in the same way as a sulfonylurea. US product labels describe use alongside diet and exercise for type 2 diabetes; this is not a general-purpose weight-loss indication.
Release type and strength
Immediate-release metformin tablets include 500, 850 and 1,000 mg strengths. Extended-release products vary; the prescribing information linked below includes 500 and 750 mg tablets and use from age 10. Check the specific product’s instructions for its strengths, approved ages and how to take it.
The boxed warning and kidney assessment
Metformin carries a boxed warning for lactic acidosis. Severe kidney impairment is a contraindication. Kidney function, acute illness, alcohol use, surgery and certain contrast procedures can affect safety. Ask the clinical team whether a temporary interruption is needed and when to restart.
Tolerability and longer-term monitoring
Diarrhea and other gastrointestinal effects are common. Metformin can lower vitamin B12, which is relevant when assessing anemia or neuropathy symptoms. Persistent adverse effects should prompt review of the actual product and regimen, not unsupervised crushing of an extended-release tablet or repeated dose changes.
Metformin in combination tablets
Janumet, Invokamet, Synjardy, Segluromet and Xigduo XR contain metformin with another ingredient. Tell the prescriber about any separate metformin tablets to avoid taking it twice unintentionally. The total metformin dose and the combination’s kidney restrictions both need checking.
Questions and answers
Is every metformin ER product labeled identically?
No. Strengths, age labeling and instructions can differ by product; check the dispensed label.
Is metformin insulin?
No. It is an oral biguanide with different mechanisms.
Can a combination tablet duplicate metformin?
Yes. Several combination tablets contain metformin. Ask the prescriber or pharmacist to check the full medicine list for duplication.
Related reading
Sources
- Metformin: official US prescribing information
- DailyMed: immediate-release metformin prescribing information
Sources checked 1 October 2026. This information does not replace advice from your healthcare professional. For complete warnings and instructions, read the product information and consult the prescribing team.
Reviewed by: Mattias Hagman, PhD
About the reviewer:
Dr Mattias Hagman (PhD, University of Sydney) has an academic background and experience working with healthcare-related content and regulated industries. He has lecturing experience at international universities, including Stockholm University and the University of Malta.
Last reviewed: October 2026