Can you take metformin without food?
If you take metformin without food you may end up with an upset stomach, especially if you are just starting treatment. Nausea and vomiting are some of the most common side effects with metformin and can occur in over 30% of patients.
When first starting treatment, your doctor will usually slowly increase your dose over a period of several weeks to help minimize the stomach side effects due to metformin.
Five of the top 7 side effects with metformin are stomach-related, and occur in the following percentages of patients:
- Diarrhea - 53%
- Nausea / vomiting (throwing up) - 26%
- Flatulence / gas - 12%
- Indigestion - 7%
- Abdominal (stomach area) discomfort or pain - 6%
Loss of appetite, metallic taste in the mouth or a taste change, abnormal stools and weight loss have also been reported as gastrointestinal (stomach) side effects with metformin.
In studies, 6% of patients (6 out of every 100) taking metformin stopped treatment due to diarrhea. But in general, these side effects tend to go away within a few weeks after starting treatment.
Metformin is usually taken once or twice per day, but your dose may be different. If you take it once a day, it’s usually recommended to take it after an evening meal. If you take it twice per day, take it after your morning and evening meals. Take it at about the same time each day.
Why does metformin cause an upset stomach?
Stomach side effects with metformin can be related to quickly increasing the dose and use of high doses. Your doctor will probably slowly increase your dose over a period of several weeks to help minimize the stomach side effects due to metformin.
If you have stomach side effects with this medicine, contact your doctor to see if your dose can be adjusted until you can better tolerate the medicine.
It's not really known why metformin leads to stomach problem but it may be related to its mechanism of increased gut mobility, serotonin-like effects, or effects due to increases in glucagon-like peptide 1 (GLP-1).
Once you get over the initial stomach side effects in a few weeks, metformin is usually well-tolerated by most people. If these side effects are severe, don't go away or are worrisome to you, you should contact your healthcare provider right away.
To learn more you can read about Metformin Warnings and Side Effects in greater detail.
Related questions
- How long does metformin take to work?
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Who uses metformin?
Metformin is approved by the FDA to help manage high blood sugar levels in people with type 2 diabetes patients. In addition, it may be used off-label to treat patients with gestational diabetes, for weight gain caused by antipsychotic medication, to prevent type 2 diabetes (prediabetes), and for treating and preventing polycystic ovary syndrome (PCOS), as noted in this review study.
Metformin comes 3 ways: as an oral immediate-release tablet, as an extended-release tablet and as an oral solution. Brand names for metformin include Glumetza, but most people use the much more affordable generic option. If you take the extended-release form, swallow it whole; do not crush, cut, split or chew the tablets.
To learn more about pricing for metformin, visit the Drugs.com Price Guide where you can compare generic and brand name drug prices and access cost-saving coupons and discount cards.
This is not all the information you need to know about metformin for safe and effective use and does not take the place of your health care provider’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.
References
- Metformin HCL extended-release [product information]. Apotex. Updated April 25, 2025. Accessed Aug 25, 2025 at https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1dc48913-f0b3-71fd-43e8-81d195af2414
- Corcoran C, Jacobs TF. Metformin. [Updated 2023 Aug 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK518983/
- Wexler D (author). Metformin in the treatment of adults with type 2 diabetes mellitus. Up to Date. Accessed July 5, 2023 at https://www.uptodate.com/contents/metformin-in-the-treatment-of-adults-with-type-2-diabetes-mellitus
Read next
Why does metformin cause diarrhea?
Metformin causes diarrhea by changing gut bacteria, affecting bile acid absorption, blocking water absorption in the intestines, and increasing gut-stimulating hormones. These combined effects make stools looser and more frequent.
Continue reading
Does metformin lower A1C, if so how much?
When metformin is used alone as monotherapy, it lowers A1C by about 1% to 2% on average. A1C is a measure of longer-term blood sugar control. In most patients, metformin is suggested as the initial treatment for type 2 diabetes, but its glucose-lowering effect may not be adequate for all patients if used alone. Continue reading
Does metformin cause weight loss?
Metformin, an oral type 2 diabetes medicine, may lead to a modest weight loss and does not usually lead to significant, if any, weight gain. In various clinical studies, when metformin was used alone, it led to a weight loss of 0.7 to 3.8 kg (1.5 to 8.4 lbs) in most patients, but other studies have shown weight loss up to 5.8 kg (12.8 lbs). Continue reading
See also:
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