Partly. In 13 randomized trials of people with type 2 diabetes, metformin lowered CRP, a common blood marker of inflammation. Two other markers, IL-6 and TNF-alpha, did not change. In people without diabetes, the effect was small or missing, and lifestyle change lowered CRP more than the pill did.
What does "anti-inflammatory" mean for a diabetes drug?
Metformin is the first drug most doctors reach for in type 2 diabetes. Its main job is blood sugar. The inflammation question comes from a hunch: that it might calm the body in other ways too.
To test that, trials measure markers in the blood. CRP, or C-reactive protein, is made by the liver and rises when the body is inflamed. IL-6 (interleukin 6) and TNF-alpha are signaling proteins that help drive inflammation. A meta-analysis is a study that pools the results of many earlier studies to get a clearer answer.
So "is metformin anti-inflammatory?" really means: when people take it, do these numbers go down?
Does metformin reduce inflammation in people with diabetes?
For CRP, the answer is yes, modestly. A 2021 meta-analysis pooled 13 randomized trials with 1,776 people who had type 2 diabetes. CRP fell after metformin. IL-6 and TNF-alpha did not change in any meaningful way. The CRP drop was clearer when people took the drug for more than 24 weeks.
In a diabetes prevention trial, CRP fell 13.2% on metformin and 34% with a lifestyle program.From a 2018 randomized trial in Psychosom Med
That split matters. CRP is a downstream marker. IL-6 sits further up the chain and helps tell the liver to make CRP. If metformin were broadly calming inflammation, you might expect IL-6 to fall as well. In these trials, it didn't.
A 2023 meta-analysis looked at people with diabetes taking metformin plus a newer drug type called an SGLT2 inhibitor. The pair lowered CRP and TNF-alpha more than metformin alone. That tells us metformin is not the strongest inflammation lever in the diabetes toolbox.
What about polycystic ovary syndrome?
Metformin is also used for polycystic ovary syndrome, or PCOS, a hormone condition that often travels with insulin resistance.
A 2017 meta-analysis of 20 studies (13 randomized trials and 7 without randomization) found CRP fell after metformin in women with PCOS, especially in women with obesity. IL-6 did not change significantly. The pattern echoes the diabetes trials.
There is a catch. Results varied widely between studies, and the authors could not find out why. Metformin also lowered body mass index in these studies. So some of the CRP drop may come from weight change, not from a direct effect on inflammation.
Is metformin good for inflammation if you don't have diabetes?
This is the question the longevity crowd cares about, and the evidence is thinner. A 2018 meta-analysis looked at six compounds tested against low-grade inflammation in middle-aged and older adults. Metformin made the list, and its effect on CRP was the smallest of the four that worked: a reduction of 0.16 mg/L. The authors urged caution because results varied across studies.
The CAMERA trial in Glasgow tested it directly. It enrolled 173 people, average age 63, who had heart disease and large waists but no diabetes. Half took 850 mg of metformin twice a day for 18 months, and half took a placebo pill. High sensitivity CRP did not differ between the groups.
The Diabetes Prevention Program gives a useful comparison. It randomized adults at high risk of diabetes to metformin, a lifestyle program or placebo. After a year, CRP fell 13.2% in the metformin group and 34% in the lifestyle group, among people not taking antidepressants. IL-6 showed no such links.
The pill moved CRP a little, while the group that changed how they lived saw a drop more than twice as large, without a prescription.
What are the downsides of metformin?
Every drug has trade-offs. The common ones are in the gut. A 2022 meta-analysis of 71 randomized trials found metformin raised the risk of abdominal pain, diarrhea and nausea compared with other treatments. Bloating and diarrhea were more likely with the immediate-release form than the extended-release form. In CAMERA, 28 people on metformin had diarrhea, nausea or vomiting, compared with 5 on placebo.
Long-term use can lower vitamin B12. A 2019 meta-analysis of 31 studies found people with diabetes on metformin had about twice the risk of B12 deficiency, and the drop grew with dose and time. The authors recommend a yearly B12 test for people with diabetes who take it.
One trial raised a flag for healthy older adults. In the MASTERS trial, healthy adults aged 65 and older did 14 weeks of strength training, 46 of them on 1,700 mg of metformin a day and 48 on a placebo. The placebo group gained more lean mass and thigh muscle. The researchers had expected metformin to help, since it was thought to calm muscle inflammation. It did the opposite for muscle growth.
We found no evidence in these trials that metformin causes inflammation.
What this means for you
Tick what you'll try this week. Your picks stay on this device.
you are thinking of starting metformin without diabetes or PCOS; you want to stop or change your dose; you have kidney or liver disease; you are pregnant, planning a pregnancy or breastfeeding; you are older and strength training; or you have numbness, tingling or tiredness that could point to low B12.
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The bottom line
Thirteen diabetes trials, twenty PCOS studies and one careful heart trial in Glasgow point the same way. Metformin can nudge CRP down in people whose blood sugar and weight it is already treating. Beyond that, the signal thins out. IL-6 and TNF-alpha stay put, and in people without diabetes CRP barely moves. So metformin is a diabetes drug with a modest side effect on one marker, not an inflammation drug. For lower CRP, the habits in the lifestyle group did more.
Common questions
Does metformin reduce inflammation in the body?
It lowers CRP modestly in people with type 2 diabetes. A 2021 meta-analysis of 13 randomized trials found CRP fell, especially after more than 24 weeks, but IL-6 and TNF-alpha did not change. In women with PCOS, CRP also fell, but not IL-6. In people without diabetes, the effect was small or absent.
Can metformin cause inflammation?
We found no evidence that it does. In the trials we reviewed, inflammation markers fell or stayed the same. Its known side effects are mainly in the gut: a 2022 review of 71 trials found more abdominal pain, diarrhea and nausea. Long-term use is also linked to lower vitamin B12.
Is metformin good for inflammation?
It is not a good tool for inflammation on its own. In 173 people with heart disease and no diabetes, 18 months of metformin did not change CRP versus placebo. In adults at risk of diabetes, a lifestyle program lowered CRP by 34% after a year, compared with 13.2% for metformin.
Should healthy people take metformin for aging?
The trials in our evidence pack do not support it. Across studies in middle-aged and older adults, its effect on CRP was small. In a trial of healthy adults aged 65 and older, people taking metformin gained less muscle from strength training than people on placebo. Starting it is a decision for you and a doctor.
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How this article was made
Researched and written from 9 peer-reviewed papers. Our automated check matched every claim against the exact words of its source, confirmed every paper exists in PubMed, and found none retracted. Checked November 1, 2026. Not individually reviewed by a doctor. Photos are illustrative; the people in them are not patients or readers.
Grades run Strong, Moderate, Emerging, Early and Not supported, and the grade decides the words we may use. How we grade evidence · Medical disclaimer
Sources
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- Meta-analysisEffect of SGLT2 Inhibitors and Metformin on Inflammatory and Prognostic Biomarkers in Type 2 Diabetes Patients.Cao Y, Liang N, Liu T et al. Endocr Metab Immune Disord Drug Targets, 2023.PubMedFull paper
- Meta-analysisEvidence-based nutritional and pharmacological interventions targeting chronic low-grade inflammation in middle-age and older adults: A systematic review and meta-analysis.Custodero C, Mankowski RT, Lee SA et al. Ageing Res Rev, 2018.PubMedFull paper
- Meta-analysisEffects of metformin treatment on serum levels of C-reactive protein and interleukin-6 in women with polycystic ovary syndrome: a meta-analysis: A PRISMA-compliant article.Wang J, Zhu L, Hu K et al. Medicine (Baltimore), 2017.PubMedFull paper
- Randomized trialMetformin for non-diabetic patients with coronary heart disease (the CAMERA study): a randomised controlled trial.Preiss D, Lloyd SM, Ford I et al. Lancet Diabetes Endocrinol, 2014.PubMedFull paper
- Meta-analysisAssociations between metformin use and vitamin B12 levels, anemia, and neuropathy in patients with diabetes: a meta-analysis.Yang W, Cai X, Wu H et al. J Diabetes, 2019.PubMedFull paper
- Meta-analysisGastrointestinal adverse events of metformin treatment in patients with type 2 diabetes mellitus: A systematic review, meta-analysis and meta-regression of randomized controlled trials.Nabrdalik K, Skonieczna-Żydecka K, Irlik K et al. Front Endocrinol (Lausanne), 2022.PubMedFull paper
- Randomized trialMetformin blunts muscle hypertrophy in response to progressive resistance exercise training in older adults: A randomized, double-blind, placebo-controlled, multicenter trial: The MASTERS trial.Walton RG, Dungan CM, Long DE et al. Aging Cell, 2019.PubMedFull paper
- Randomized trialDepressive Symptoms, Antidepressant Medication Use, and Inflammatory Markers in the Diabetes Prevention Program.de Groot M, Marrero D, Mele L et al. Psychosom Med, 2018.PubMedFull paper
