Short answer

We found no documented interaction between Biotin and L-theanine in the sources below. That isn't proof the combination is right for you: check each one's cautions, and ask your pharmacist if you take medication.

Biotin

What it is: A B vitamin that helps turn the food you eat into energy.

What the research says: It's widely sold for hair, skin and nails, but there's little evidence for that. A few small studies found harder nails in people with brittle nails.

Cautions

• High-dose biotin can make some lab tests wrong, including thyroid hormone tests. Tell your clinician before a blood test.

Medicines to check

• Long-term anti-seizure medicines can lower biotin levels

In Holitro: Biotin 5000mcg (5000 mcg per capsule)

Source: NIH Office of Dietary Supplements: Biotin: Fact Sheet for Consumers (updated January 2021)

L-theanine

What it is: An amino acid found in green tea, taken for calm and sleep.

What the research says: Small studies suggest it may improve sleep; results for anxiety are mixed.

Cautions

• No side effects have been reported for the supplement.
• It may not be safe in pregnancy or while breastfeeding.

Medicines to check

• Sleep medicines and sedatives (such as lorazepam, diazepam or zolpidem): may add to drowsiness

In Holitro: Theanine 200mg (200 mg per capsule)

Source: Memorial Sloan Kettering Cancer Center, About Herbs: L-Theanine (updated July 2026)

Check with your doctor or pharmacist, especially if you take medication.

Check your stack — free

Educational information only, not medical advice. This reflects general ingredient overlap, not a personalized safety review. Always check with your doctor or pharmacist before combining supplements, especially if you take medication, are pregnant or nursing, or manage a health condition. These statements have not been evaluated by the FDA.