Awaiting clinical review. This entry is sourced but has not yet been signed off by a pharmacist or clinician.

Ocimum tenuiflorum (leaf)

Holy basil (tulsi)

Holy basil may reduce perceived stress, but the evidence is one modest industry-funded trial and a handful of small, mostly weak studies, so it is too early to call it proven. Trials of up to 13 weeks report few side effects, and its blood-sugar effect looks promising but rests on low-quality studies. The main caution is that long-term safety and pregnancy safety have not been studied, and it may add to diabetes medication.

Written by

Healthy and Herbal editorial team

Updated

29 September 2026

A holy basil (tulsi) plant with green and purple leaves

At a glance

Last reviewed 29 September 2026

Evidence

Limited

Best for

Everyday stress

Typical form & use

Leaf extract, 125 mg twice daily

Onset

4+ weeks

Safety

Long-term safety unstudied; check with diabetes drugs. 1 known interaction, most serious with diabetes medication.

Check with your medications →

What it's used for

Evidence is rated per use. The same ingredient can be strong for one thing and traditional for another.

Use	Evidence	What the research shows
Everyday stress	Limited	One 8-week, double-blind, placebo-controlled trial of 100 stressed adults found 125 mg of a standardised leaf extract twice daily improved Perceived Stress Scale scores (p = 0.003) and lowered hair cortisol (p = 0.025) compared with placebo. The trial was funded by the extract's manufacturer. A systematic review of herbs and cortisol concluded that effects on the stress axis were unclear for most plants, holy basil included. Older stress trials are small and mostly lower quality.^1,2,3
Generalised anxiety	Traditional	A single uncontrolled trial of 35 people with generalised anxiety disorder took 500 mg of leaf extract twice daily for 60 days and reported lower anxiety scores. With no placebo group it cannot show the herb caused the change, so this is closer to a traditional-use rating than a tested one.^4,2
Blood sugar in type 2 diabetes	Limited	A 2017 systematic review found 10 small trials in type 2 diabetes or metabolic syndrome, mostly 2 to 13 weeks long, generally reporting lower fasting and after-meal glucose. Only about a third of all 24 studies in the review were high quality, few were double-blind, and doses and preparations varied. A 2005 review of Ayurvedic diabetes herbs judged holy basil to have suggestive evidence that deserves further study, not proof.^2,5
Sleep quality	Traditional	The same stress trial saw better Athens Insomnia Scale scores on holy basil, but the authors say gold-standard objective sleep measurement is needed to confirm this. It was a secondary finding.¹

How much

Ranges below are what studies used and what supplements commonly contain. They are not a recommendation for you. Start at the low end.

Best-tested extract

125 mg twice daily¹

Standardised leaf extract used in the 8-week stress trial.

Other studied doses

500 mg twice daily^4,2

Leaf extract capsules used for 60 days in the anxiety study. The systematic review lists daily leaf powder from about 2 to 3 g in blood-sugar studies, and a 300 mg twice-daily extract with diabetes medication.

Longest duration studied

13 weeks²

The systematic review notes the longest study lasted 13 weeks, so the absence of reported side effects says nothing about longer use.

Upper limit

Not established²

None of the sources we opened set a safe maximum dose.

Timing · The stress trial gave doses twice daily. Several blood-sugar and anxiety studies had doses taken before or after meals, but none compared timings.With food? · No source tested food against no food. The anxiety trial gave capsules after meals, and one obesity trial reported mild nausea.How long to trial · The stress trial judged effects at 8 weeks, and the anxiety study at 30 and 60 days, so give any product several weeks before deciding it does nothing.

How people take it

Standardised leaf extract capsule125 mg twice daily (stress trial)The form with the best trial. Extracts vary between makers, so the result does not carry over to every product.

Leaf powder or capsuleAbout 2–3 g powder daily (blood-sugar studies)Used in the small diabetes trials; product details were often not reported.

Tea (tulsi leaf)No tested doseThe traditional form, but the sources we read did not test tea for stress or blood sugar, so its effect is unknown.

Safety

Who should avoid

Pregnancy and breastfeeding — no safety data in the sources we read
Taking diabetes medication — glucose may drop further, tell your prescriber
Long-term daily use — nothing studied beyond 13 weeks
Children — no studies in the sources we read

Known interactions

MonitorDiabetes medication — In a 13-week trial, adding holy basil to glibenclamide lowered HbA1c and glucose further than the drug alone, so the effects may add together.

Questions people ask

Does holy basil reduce stress and anxiety?

One 8-week placebo-controlled trial found lower perceived stress and hair cortisol, but it was manufacturer-funded and a systematic review called the effect on cortisol unclear. Evidence for anxiety disorders is a single uncontrolled study, so it is not a substitute for treatment.

Can holy basil lower blood sugar?

Small trials in type 2 diabetes generally report lower glucose, but most were short and of low quality, so the size of any effect is unknown. If you take diabetes medication, mention it to your prescriber first because the effects may add together.

Is holy basil safe to take daily?

Studies lasting up to 13 weeks reported no significant adverse events, with occasional mild nausea in one trial. Longer-term safety has not been studied, and safety in pregnancy is unknown.

Is holy basil the same as ordinary basil?

No. Holy basil, or tulsi, is Ocimum tenuiflorum, a different species from the sweet basil used in cooking. The trials discussed here used holy basil leaf, so results do not apply to culinary basil.

Sources

Last reviewed 29 September 2026 · Next review March 2027 · How we rate evidence