The short answer
Not known in people. We found no study of ashwagandha taken with metformin or insulin in people. The US National Center for Complementary and Integrative Health (NCCIH) lists diabetes medicines among those ashwagandha might interact with, but gives no details or numbers.
The only study of ashwagandha with metformin was in diabetic mice. It focused on thyroid hormones. Metformin lowered them, and ashwagandha brought them back towards normal. It also measured blood sugar, but its published summary does not say whether ashwagandha lowered sugar further on top of metformin. If you take metformin or insulin, tell your prescribing doctor before you start ashwagandha, and ask whether you should check your sugar more often.
Metformin is sold in India as Glycomet and Glycomet SR, and Glycomet-GP also contains glimepiride. Insulins include Actrapid, Lantus and NovoRapid.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| Named by a US health agency as a possible interaction with diabetes medicines[1] | Not stated | Not quantified | Theoretical by mechanism |
| Ashwagandha restored thyroid hormones lowered by metformin in diabetic mice[2] | Not established | Raised T3 and T4; no blood sugar interaction shown | Animal |
| Liver injury from ashwagandha products[3][4] | Not established | Herb safety context, not an interaction | Case report |
No listing is not a clearance. A missing interaction here never means a combination is safe.
The evidence, study by study
Mouse study, Indore, 2009 Animal
At Devi Ahilya University, mice made diabetic with dexamethasone were given metformin (150 mg/kg), which further lowered their thyroid hormone T4. Adding an ashwagandha extract (1.4 g/kg) brought T3 and T4 back to normal levels. The study did not report how ashwagandha changed blood sugar on top of metformin. Animal results show the question is worth asking. They cannot tell us what happens in people.[2]
Case series, India, 2023 Case report
Liver specialists at several Indian centres described 8 people with liver injury after single-herb ashwagandha products, out of 23 ashwagandha cases seen between 2019 and 2022. Five already had chronic liver disease, and three of them developed acute-on-chronic liver failure and died. This is about ashwagandha's own risk to the liver, not about diabetes medicines.[3]
Case series, Iceland and the United States, 2020 Case report
Five people developed jaundice 2 to 12 weeks after starting supplements containing ashwagandha. Their liver tests returned to normal within 1 to 5 months in four of them; the fifth was lost to follow-up. Four were also taking other supplements.[4]
What your doctor may watch for
- Blood sugar readings and any symptoms of low sugar. The metformin label asks you to tell your doctor about any herbal supplements you take.[5]
- Yellow eyes or skin, dark urine, itching or nausea, which can be signs of liver injury.[4]
What to tell your prescribing doctor
You can read this out, or show them this page:
“I am taking, or planning to take, ashwagandha (name of product, form and how much) along with my diabetes medicine. A US health agency lists diabetes medicines among those ashwagandha might interact with. Should I check my blood sugar more often?”
Withheld until review
Questions people ask
Is KSM-66, a gummy or ashwagandha tea any different?
They are different products, and none of them has been tested with metformin or insulin. Some gummies and blends add other ingredients, so read the full label.[1]
Does taking them at different times help?
We found no study that tested a time gap between ashwagandha and metformin or insulin, so there is no evidence that spacing them helps. That is a question for your doctor.[1]
Related
Type 2 diabetes (sugar): what Ayurveda offers
Some herbs, such as methi and karela, lowered HbA1c a little in trials. Taken with diabetes medicines, they can add to the risk of low sugar.
InteractionAmla and metformin
Amla lowered blood sugar further alongside metformin in one small rat study. Nobody has tested the two together in people.
InteractionAshwagandha and thyroid medicines
Ashwagandha can raise thyroid hormone levels. That could add to levothyroxine, or work against antithyroid drugs.
InteractionGiloy with metformin or insulin
Not tested in people. In rats, two weeks of giloy extract raised metformin levels. Giloy also carries its own risk of liver injury.
Sources
- National Center for Complementary and Integrative Health (US). Ashwagandha.
- Jatwa R, Kar A. Amelioration of metformin-induced hypothyroidism by Withania somnifera and Bauhinia purpurea extracts in type 2 diabetic mice. Phytother Res. 2009;23(8):1140-1145. PMID 19170137.
- Philips CA, Valsan A, Theruvath AH, Ravindran R, Oommen TT, Rajesh S, Bishnu S, Augustine P; Liver Research Club India. Ashwagandha-induced liver injury: a case series from India and literature review. Hepatol Commun. 2023;7(10):e0270. PMID 37756041.
- Björnsson HK, Björnsson ES, Avula B, Khan IA, Jonasson JG, Ghabril M, Hayashi PH, Navarro V. Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver Int. 2020;40(4):825-829. PMID 31991029.
- Metformin hydrochloride tablets, US prescribing information (DailyMed).
Awaiting review by The Good Vaidya Medical Board. Prepared from the sources below and checked against each one.
Published 4 November 2026 · Last updated 4 November 2026
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