Short answer

We found no documented interaction between CoQ10 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.

CoQ10

What it is: A compound the body makes, found at high levels in the heart, liver and kidneys.

What the research says: Studies on heart disease are inconclusive. Overall, it doesn't seem to relieve muscle pain from statins, and it probably doesn't lower blood pressure meaningfully.

Cautions

• No serious side effects reported; it can cause mild insomnia or stomach upset.

Medicines to check

• Warfarin (blood thinner) and insulin
• Some cancer treatments: check with your care team

In Holitro: CoQ10 (200 mg per capsule)

Source: NIH National Center for Complementary and Integrative Health: Coenzyme Q10 (updated January 2019)

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.