The short answer
Possibly, though tulsi's own part is not clear. A 56-year-old man who had been stable on warfarin for 12 years had an INR of 5.45 after taking a herbal kadha. Holy basil was one of many ingredients, so the report cannot show that tulsi caused it. A raised INR means blood takes longer to clot, which raises the risk of bleeding.
We found no study of tulsi alone with warfarin. The Merck Manual cautions about taking holy basil with medicines that slow clotting, and the warfarin label asks for extra INR tests when any herbal product is started or stopped. If you take warfarin or acenocoumarol, tell your prescribing doctor before you start tulsi or a kadha, and ask whether your INR should be checked more often.
Warfarin is sold in India as Warf. Acenocoumarol, a related blood thinner, is sold as Acitrom.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| INR of 5.45 after a multi-herb kadha that included tulsi[1] | Not established; many ingredients | Stronger blood-thinning effect | Case report |
| Possible added bleeding risk[2] | Holy basil may slow clotting (proposed, not shown in people) | More risk of bleeding | Theoretical by mechanism |
No listing is not a clearance. A missing interaction here never means a combination is safe.
The evidence, study by study
Case report, 2021 Case report
A 56-year-old man who had taken warfarin for 12 years, with a stable INR, developed an INR of 5.45 after drinking a kadha, a herbal decoction. The full report lists holy basil among many ingredients. Because the kadha was a mixture, the report cannot say which herb, if any one of them, was responsible.[1]
What your doctor may watch for
- Your INR, with extra tests when you start or stop any herbal product, including a kadha.[3]
- Unusual bruising or bleeding.[2]
What to tell your prescribing doctor
You can read this out, or show them this page:
“I am taking, or planning to take, tulsi (tea, kadha, capsules or extract, and how much) along with my blood thinner. There is a report of a high INR after a kadha that contained tulsi. Should my INR be checked more often?”
Withheld until review
Questions people ask
Can I drink tulsi tea while on warfarin?
Nobody has studied tulsi tea with warfarin. Tea, kadha, capsules and extracts may differ, and none has been tested on its own. Mention any tulsi you take regularly, including tea, when your INR is checked.[1][3]
Is kadha a problem with blood thinners?
The case on this page involved a kadha made of many herbs, and it was not possible to say which one raised the INR. Tell your doctor about any kadha you drink, with its ingredients if you know them.[1]
Related
Turmeric and blood thinners
Two reports describe a raised INR after turmeric in people on warfarin-type blood thinners. Blood thinners leave little margin.
InteractionGinger (adrak) and warfarin
Two women on blood thinners had a high INR after ginger supplements, and ginger users on warfarin reported more bleeding. One small study found no change.
FormulationTulsi cough syrups
Tulsi cough syrups are branded mixes, not one recipe. One contains ephedra. Most contain mulethi, and some honey or a lot of sugar.
InteractionGarlic and blood thinners (warfarin, aspirin, clopidogrel)
Health agencies warn garlic supplements may raise bleeding risk. Two small studies on warfarin found no effect, but they cannot rule out rarer bleeding.
Sources
- Premchand RK, Samnani N. Case report on interaction of warfarin with herbal medicine "kadha". IHJ Cardiovasc Case Rep. 2021;5(2):116-118. PMID 40477485.
- Merck Manual, Consumer Version. Holy Basil. Reviewed July 2025.
- Warfarin sodium 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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