Tulsi (Holy Basil)
Summary
Tulsi (holy basil) is an Ayurvedic herb. Two placebo-controlled trials of standardized extracts found lower stress scores after 6 to 8 weeks, one also with better sleep ratings and lower hair cortisol (grade B). Cognition and immune data come from single small trials. A systematic review found no significant adverse events, but the longest study lasted 13 weeks.
Key facts
- An aromatic herb indigenous to the Indian subcontinent, used in Ayurvedic and Siddha medicine[4]
- Perceived Stress Scale scores improved more than placebo with 125 mg twice daily of a standardized extract over 8 weeks (n = 100)[1]
- Athens Insomnia Scale scores improved versus placebo in the same 8-week trial[1]
- 24 human studies with 1,111 participants; only three trials had 100 or more people[4]
- No significant adverse events across the 24 studies; one trial reported transient mild nausea; longest study 13 weeks[4]
- 4 graded human outcomes on this page
- October 13, 2026
How it works
ProposedTulsi is described as an adaptogen. In the 8-week Holixer trial, the extract lowered hair cortisol and blunted salivary cortisol, salivary amylase and blood-pressure responses to a laboratory stress test, consistent with dampened stress-axis activity. Which constituents act, and how, has not been established in people.[1][4]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Stress | Grade B | Improved | RCT · n = 150 · 2012 | 2 rows |
| Cognition | Grade D | Improved | RCT · n = 40 · 2015 | 1 row |
| Immune | Grade D | Improved | Crossover RCT · n = 22 · 2011 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| General stress symptoms | Improved | Grade B | RCT · n = 150 · 2012 Adults with general stress symptoms Form: Ocimum tenuiflorum extract (OciBest) · Dose: 1,200 mg of actives per day · Duration: 6 weeks Total stress-symptom scores fell significantly more than with placebo (39% greater improvement), including forgetfulness, exhaustion and recent sleep problems. No adverse events reported. | 21977056 (opens PubMed)Source [2] |
| Perceived stress, sleep and cortisol in stressed adults | Improved | Grade B | RCT · n = 100 · 2022 Adults aged 18–65 experiencing stress Form: Standardized Ocimum tenuiflorum extract (Holixer) · Dose: 125 mg twice daily (250 mg/day) · Duration: 8 weeks Perceived Stress Scale (P = 0.003) and Athens Insomnia Scale (P = 0.025) improved more than with placebo; hair cortisol was lower at week 8, and cortisol, amylase and blood-pressure responses to a lab stress test were blunted. Well tolerated. | 36185698 (opens PubMed)Source [1] |
| Reaction time and errors on memory and attention tests | Improved | Grade D | RCT · n = 40 · 2015 Healthy men aged 18–30 (India) Form: Ethanolic leaf extract of Ocimum sanctum · Dose: 300 mg/day · Duration: 30 days Reaction times and error rates on the Sternberg and Stroop tests improved more than with placebo, and P300 latency differed between groups; cortisol and anxiety improved only within the extract group. | 26571987 (opens PubMed)Source [5] |
| Immune cytokines and cell counts in healthy adults | Improved | Grade D | Crossover RCT · n = 22 · 2011 Healthy volunteers (New Delhi, India) Form: Ethanolic extract of Tulsi leaves · Dose: 300 mg/day on an empty stomach · Duration: 4 weeks Interferon-γ, IL-4, T-helper cell and NK-cell percentages rose versus placebo. | 21619917 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Standardized leaf extracts (Holixer, OciBest) | Varies[1][2] | No human absorption data on this page.[1] | Well tolerated with no major adverse effects over 8 weeks; no adverse events reported over 6 weeks.[1][2] | Stress and sleep (250–1,200 mg/day) |
| Ethanolic leaf extract capsules | Varies[3][5] | No human absorption data on this page.[3] | The 2017 review found no significant adverse events across the human studies it covered.[4] | Cognition and immune markers (300 mg/day) |
| Leaf, tea and decoction | Varies[4] | No human absorption data on this page.[4] | The 2017 review found no significant adverse events across forms, with one report of transient mild nausea.[4] | Mixed outcomes in older and smaller studies |
Studied doses
Doses studied in human trials ranged from 250 mg/day (125 mg twice daily) to 1,200 mg/day of extract for 4 to 8 weeks in the trials cited here; across all reviewed studies the longest lasted 13 weeks.[1][2][5][4]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Diabetes medicines
- In the 2017 review, tulsi added to glucose-lowering medication lowered HbA1c more than medication alone, so combined use can change blood-sugar control.[4]
- Pregnancy and breastfeeding
- The cited trials enrolled adults and report no data on pregnancy or breastfeeding.[4]
- Long-term use
- The longest study lasted 13 weeks, so absence of reported side effects does not establish long-term safety.[4]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Extract vs leafPositive stress trials used standardized extracts at 250–1,200 mg/day; tea and raw-leaf amounts are not comparable.[1][2]
- Species namesOcimum tenuiflorum (or O. sanctum) includes distinct cultivars such as Rama and Krishna tulsi, and some sources also call Ocimum gratissimum tulsi; most papers do not specify the cultivar.[4]
- Label dose vs studied doseThe 8-week trial used 125 mg twice daily of one branded extract; doses of other extracts are not interchangeable.[1]
Cost per studied dose, without the sales pitch
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Cost per studied dose
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Frequently asked questions
Is tulsi the same as holy basil?
Yes. Tulsi is the common Indian name for holy basil, Ocimum tenuiflorum (also called O. sanctum).[4][1]
Does holy basil reduce stress?
Two placebo-controlled trials (100 and 150 adults) found standardized extracts lowered stress scores after 6–8 weeks.[1][2]
Does tulsi help sleep?
In an 8-week trial, insomnia scale scores improved more than placebo; wrist-tracker sleep was also measured but the abstract highlights the questionnaire result.[1]
How much holy basil was studied?
250 mg/day (125 mg twice daily) of Holixer, 1,200 mg/day of OciBest actives, and 300 mg/day of ethanolic extracts.[1][2][5]
Does tulsi improve memory?
One 30-day trial in 40 young men found faster, more accurate responses on memory and attention tests than placebo.[5]
Is tulsi safe?
A 2017 review of 24 studies found no significant adverse events, with one report of mild nausea, but no study lasted longer than 13 weeks.[4]
Sources
- [1]A randomized, double-blind, placebo-controlled trial investigating the effects of an Ocimum tenuiflorum (Holy Basil) extract (Holixer(TM)) on stress, mood, and sleep in adults experiencing stress.. Front Nutr, 2022. RCT
- [2]Efficacy of an Extract of Ocimum tenuiflorum (OciBest) in the Management of General Stress: A Double-Blind, Placebo-Controlled Study.. Evid Based Complement Alternat Med, 2012. RCT
- [3]Double-blinded randomized controlled trial for immunomodulatory effects of Tulsi (Ocimum sanctum Linn.) leaf extract on healthy volunteers.. J Ethnopharmacol, 2011. crossover-RCT
- [4]The Clinical Efficacy and Safety of Tulsi in Humans: A Systematic Review of the Literature.. Evid Based Complement Alternat Med, 2017. systematic-review
- [5]Holy basil (Ocimum sanctum Linn.) leaf extract enhances specific cognitive parameters in healthy adult volunteers: A placebo controlled study.. Indian J Physiol Pharmacol, 2015. RCT
What changed
- Strict second-pass self-review (no separate reviewer could be dispatched for this batch): all 5 PMIDs re-verified by NCBI esummary (titles and years match the record) and efetch checked for retraction, expression-of-concern and erratum flags (none flagged); every evidence row, key fact, form, dose, label line, FAQ and insight re-read against its abstract, and against PMC full text where the dose or count lives. Fixes: removed an unverified country; cultivar note rewritten from the review full text; pregnancy and tolerance statements narrowed to what the sources say. Page set indexable.
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year from the record) and abstracts read for each cited row. Participant totals, study sizes, adverse-event and diabetes-drug details from the PMC full text of the 2017 systematic review (PMC5376420); cognition trial recruitment (44 men) from the journal PDF. No NIH ODS or NCCIH fact sheet covers tulsi.