Short answer

We found no documented interaction between Vitamin D3 with A, E and K2 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.

Vitamin D3 with A, E and K2

What it is: A combination of vitamin D3 with vitamins A, E and K2. Vitamin D helps the body absorb calcium and supports muscles, nerves and the immune system.

What the research says: Getting enough vitamin D and calcium helps protect against osteoporosis.

Cautions

• Adults shouldn't exceed 4,000 IU (100 mcg) of vitamin D a day from all sources unless a clinician advises more. Too much can cause nausea, weakness, confusion and kidney stones.
• Too much preformed vitamin A can cause headaches and blurred vision, and birth defects in pregnancy.
• High-dose vitamin E supplements may raise bleeding risk.

Medicines to check

• Warfarin: vitamin K and vitamin E both matter, and vitamin K intake should stay steady
• Statins, steroids, orlistat and thiazide diuretics (vitamin D notes)
• Vitamin A-based medicines such as acitretin

In Holitro: D Complex (5,000 IU per capsule)

Sources: NIH Office of Dietary Supplements: Vitamin D: Fact Sheet for Consumers (updated November 2022); NIH Office of Dietary Supplements: Vitamin A: Fact Sheet for Consumers (updated March 2025); NIH Office of Dietary Supplements: Vitamin E: Fact Sheet for Consumers (updated March 2021); NIH Office of Dietary Supplements: Vitamin K: Fact Sheet for Consumers (updated March 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.