The short answer
Not known in people. In rats given a giloy (guduchi, Tinospora cordifolia) extract twice a day for two weeks, more metformin built up in the blood, it lasted longer, and the kidneys cleared less of it. Nobody has measured this in people, and we found no study of giloy with insulin.
Giloy also has its own liver risk. A study from 13 Indian centres described 43 people with giloy-linked liver injury, four of whom died, and in a smaller series some of those affected had type 2 diabetes. If you take metformin or insulin, tell your prescribing doctor before you start giloy, and ask whether your sugar and liver tests should be checked.
Metformin is sold in India as Glycomet. Insulins include Actrapid, Lantus and NovoRapid.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| Higher metformin exposure and longer half-life after two weeks of giloy extract (rats)[1] | Less clearance by the kidneys; competition for the OCT2 transporter proposed from computer modelling | More metformin in the blood | Animal |
| Liver injury linked to giloy in 43 people across 13 Indian centres[2][4] | Immune-mediated injury suspected | Hepatitis, sometimes severe; not an interaction with diabetes drugs | Observational |
| Autoimmune-like hepatitis after giloy in six people, some with type 2 diabetes[3] | May trigger or unmask autoimmune liver disease | Hepatitis; not an interaction with diabetes drugs | Case report |
No listing is not a clearance. A missing interaction here never means a combination is safe.
The evidence, study by study
Two rat studies, 2025 Animal
Two experiments each used 18 rats in three groups of six. Some rats got a single dose of an alcohol-and-water giloy extract with metformin; others got the extract twice a day for 13 days, then with metformin on day 14. With the repeated higher dose, metformin's total exposure (AUC) and half-life rose, and its clearance by the kidneys fell. The authors suggest giloy competes with metformin for a kidney transporter called OCT2, based on computer modelling. Rat results cannot tell us how much this matters in people.[1]
Study across 13 Indian centres, 2022 Observational
Doctors looked back at 43 people who developed liver injury after taking giloy between April 2020 and July 2021. Symptoms began a median of 46 days after starting it, and giloy was judged the probable cause in 67.4%. Four people died and two needed a liver transplant. The study did not look at diabetes medicines, and it cannot say how common the injury is.[2]
Case series, 2021 Case report
Six people developed liver injury after taking giloy as an immune booster during the 2020 pandemic, for a median of 90 days. Liver biopsies looked like autoimmune hepatitis. Four people may have had a hidden autoimmune liver disease that giloy brought out, and these four also had hypothyroidism and type 2 diabetes. Six cases cannot show how often this happens.[3]
What your doctor may watch for
- Blood sugar readings.[5]
- Kidney and liver function, which the metformin label asks your doctor to review, especially after an illness.[5]
- Yellowing of the eyes or skin (jaundice) after starting giloy.[4]
What to tell your prescribing doctor
You can read this out, or show them this page:
“I take metformin or insulin (name and dose), and I am taking, or planning to take, giloy (juice, tablets, powder or kadha, and how much). In rats giloy raised metformin levels, and giloy can cause liver injury on its own. Should my sugar, kidney or liver tests be checked?”
Withheld until review
Questions people ask
Related
Giloy and paracetamol (Dolo, Crocin)
Not tested together. Giloy is a known cause of liver injury, and the paracetamol label warns people with liver disease. The combined effect is unknown.
ConditionType 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.
InteractionFenugreek (methi) with metformin or insulin
Methi lowered blood sugar further when added to diabetes medicines in two trials. How often that causes low sugar was not measured well.
InteractionNeem and diabetes medicines (metformin, insulin)
In a 12-week trial, a neem leaf and twig extract lowered blood sugar further in people already on metformin. Insulin was not studied.
Sources
- Sahu R, Gaur M, Subudhi BB. Enhancement of metformin bioavailability by Tinospora cordifolia extracts: insights into pharmacokinetic interactions. Indian J Nat Prod Resour. 2025;16:258-270.
- Kulkarni AV, Hanchanale P, Prakash V, Kalal C, Sharma M, Kumar K, Bishnu S, Kulkarni AV, Anand L, Patwa AK, Kumbar S, Kainth S, Philips CA; Liver Research Club India. Tinospora cordifolia (giloy)-induced liver injury during the COVID-19 pandemic: multicenter nationwide study from India. Hepatol Commun. 2022;6:1289-1300. PMID 35037744.
- Nagral A, Adhyaru K, Rudra OS, Gharat A, Bhandare S. Herbal immune booster-induced liver injury in the COVID-19 pandemic: a case series. J Clin Exp Hepatol. 2021;11:732-738. PMID 34230786.
- LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. Tinospora. Updated 27 June 2025.
- Metformin hydrochloride tablets, US prescribing information (DailyMed).
Updated 4 November 2026
Taking giloy with other medicines? A vaidya can check your full list.
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