Holy Basil and medications.
Holy Basil is in the Distil supplement database, evidence Grade B. The page below lists every medication we have explicitly assessed it against.
Holy basil, or tulsi, is Ocimum tenuiflorum, a plant long used in Ayurvedic practice and now studied as an adaptogen. It carries Grade B evidence across stress, cognition, and blood glucose. Small controlled trials suggest it may support cortisol and stress modulation, ease anxiety and low mood, and help regulate blood sugar, and one crossover RCT found shifts in immune markers. The honest limit is that most studies are small and short, so the picture is promising rather than settled, and it sits as a companion to better-evidenced adaptogens like ashwagandha rather than a replacement. On the interaction side, two points matter. It has a mild antiplatelet effect, so caution applies with anticoagulants, mainly at high doses. It may also modulate thyroid activity, which means anyone with a thyroid condition should monitor rather than assume it is neutral. Safety overall is good, with mild stomach upset the most common issue. A reasonable adjunct for stress, used with awareness if you take blood thinners or have thyroid problems.
Below are the 9 documented pairs we have explicitly assessed for Holy Basil: 9 amber. The pairs cluster around 2 mechanisms: Additive glucose lowering and Reduced thyroid-hormone effect. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not listed here is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by medication, and the missing-item form at the bottom of the page routes any uncatalogued medication into our next curation pass.
Documented interactions
Last reviewed 17 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
Additive glucose lowering
Amber Does interact with Empagliflozin?
Holy basil (tulsi) may lower blood sugar on its own. Empagliflozin also lowers blood sugar, so the two may add up. The combination is usually manageable because empagliflozin rarely causes low blood sugar on its own, but monitor your glucose when you start holy basil or change the dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Gliclazide?
Holy basil (tulsi) may lower blood sugar on its own. Gliclazide already lowers blood sugar and carries the highest risk of pushing it too low among the common diabetes tablets, so taking the two together may add up. If you take both, monitor your blood glucose, especially in the first few weeks, and your doctor may need to adjust the gliclazide dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Glimepiride?
Holy basil (tulsi) may lower blood sugar on its own. Glimepiride is a sulfonylurea that already lowers blood sugar and carries one of the highest risks of pushing it too low, so taking the two together may add up. If you take both, monitor your blood glucose, especially in the first few weeks, and your doctor may need to adjust the glimepiride dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Insulin aspart?
Holy basil (tulsi) may lower blood sugar on its own, on top of the insulin you inject. This may increase the chance of glucose going too low. If you take holy basil with insulin, monitor your blood glucose closely, especially early on, and your doctor may need to reduce your insulin dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Insulin glargine?
Holy basil (tulsi) may lower blood sugar on its own, on top of the insulin you inject. This may increase the chance of glucose going too low. If you take holy basil with insulin, monitor your blood glucose closely, especially early on, and your doctor may need to reduce your insulin dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Metformin?
Holy basil (tulsi) may lower blood sugar on its own. Metformin also lowers blood sugar, so the two may add up. The combination is generally manageable because metformin on its own rarely causes low blood sugar, but monitor your glucose when you start holy basil or change the dose, and your doctor may adjust the metformin if needed.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Pioglitazone hydrochloride?
Holy basil (tulsi) may lower blood sugar on its own. Pioglitazone also lowers blood sugar by improving insulin sensitivity, so the two may add up. The combination is usually manageable, but monitor your glucose when you start holy basil or change the dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Amber Does interact with Sitagliptin?
Holy basil (tulsi) may lower blood sugar on its own. Sitagliptin also lowers blood sugar, so the two may add up. The combination is usually manageable because sitagliptin rarely causes low blood sugar on its own, but monitor your glucose when you start holy basil or change the dose.
Evidence: Limited human data, based on case reports and a known mechanism.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
Reduced thyroid-hormone effect
Amber Does interact with Levothyroxine?
Holy basil (tulsi) has been reported to lower the thyroid hormone thyroxine (T4), though this has only been shown in animals and not in people. If you take levothyroxine, the concern is that holy basil could work against it and let some underactive-thyroid symptoms come back. There is no proof this happens in humans, but because your thyroid dose is finely balanced, tell the clinician who manages your thyroid before starting holy basil and ask for a TSH check a few weeks later so your dose can be reviewed if needed.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope. Use the checker below to surface any medication, and submit a missing item if you take something we have not catalogued.
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How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
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The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
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- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
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