The short answer
Not known in people. We found no study of tulsi with fertility medicines such as clomiphene or letrozole, or with IVF. The only related study was in rats: 15 days of tulsi leaf extract raised progesterone, a female reproductive hormone, though the rats' cycles did not change significantly.
The authors concluded that tulsi impaired fertility, but they never tested whether the rats could still get pregnant, and a published letter pointed this out. Rat results cannot tell us what happens in people. If you are trying to conceive or are in fertility treatment, tell your fertility doctor before you start a tulsi supplement, and ask whether it fits with your treatment plan.
Clomiphene is sold in India as Clofert and letrozole as Letroz. Injected hormones used in IVF include Gonal-F and Hucog.
At a glance
| What was seen | How it may work | Direction | Evidence |
|---|---|---|---|
| Tulsi leaf extract raised progesterone in female rats[1][2] | Hormonal change; route not established | Unknown for fertility medicines or IVF in people | Animal |
No listing is not a clearance. A missing interaction here never means a combination is safe.
The evidence, study by study
Rat study, 2019 Animal
Female rats were given tulsi leaf extract, or eugenol, a compound found in tulsi, for 15 days. The extract raised progesterone but did not significantly change the length of the oestrous cycle. Eugenol lengthened the cycle. The authors concluded that both impaired fertility, though the extract and eugenol results differed, and the abstract does not say how many rats were used. Animal results show the question is worth asking. They cannot tell us what happens in people.[1]
What your doctor may watch for
- There is no tested monitoring plan for tulsi during fertility treatment. Your fertility team can decide whether any hormone tests are needed, and the Merck Manual lists pregnancy among its cautions for holy basil.[3]
What to tell your prescribing doctor
You can read this out, or show them this page:
“I am taking, or planning to take, tulsi (name of product, whether it is tea, capsules or an extract, and how much) while trying to conceive. A rat study found tulsi leaf extract changed progesterone levels. Does it fit with my fertility treatment, or should I hold off?”
Withheld until review
Questions people ask
Can I drink tulsi tea during IVF?
Nobody has studied it. The rat study used a concentrated leaf extract, not tea, and no study has compared the two in fertility treatment. Tulsi in food or a cup of tea is a different exposure, but it has not been tested either, so ask your fertility doctor.[1]
Related
PCOS and PCOD: what Ayurveda offers
Curcumin improved blood sugar markers, and periods a little, in small trials. Most Ayurveda studies of PCOS are single case reports.
InteractionTulsi and metformin
Holy basil leaves lowered blood sugar in a 1996 trial in type 2 diabetes. With metformin, sugar could fall further. The pair has not been studied.
InteractionTulsi and blood thinners like warfarin
A man on warfarin had a high INR after a herbal kadha that included tulsi. Tulsi's own role is not clear, and it has not been studied alone.
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.
Sources
- Poli V, Challa C. A comparative study of eugenol and Ocimum sanctum Linn. leaf extract on the antifertility effect in female albino rats. J Chin Med Assoc. 2019;82(3):231-234. PMID 30908416.
- Li YT, Yeh CC, Wang PH. Without mating test, it is hard to say that the reproductive performance of rats is decreased. J Chin Med Assoc. 2019;82(11):884. PMID 31305348.
- Merck Manual, Consumer Version. Holy Basil. Reviewed July 2025.
Updated 4 November 2026
Taking tulsi with other medicines? A vaidya can check your full list.
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