← NUTRITIONFoundational

Vitamin D3

Worth it if you're low or short on sun — not a performance booster if your levels are already fine.

EVIDENCE
Strong
TYPICAL DOSE
1,000–2,000 IU daily is a common maintenance range; test and dose to your own blood levels where you can
TIMING
With a meal that contains some fat, which improves absorption. Time of day doesn't matter.
WHAT IT IS

A hormone-like vitamin your skin makes from sunlight, involved in bone health, immune function and muscle. Deficiency is common in northern latitudes and through winter.

WHY (OR WHY NOT)

Correcting a genuine deficiency supports bone and immune health and can help with strength in people who were low to begin with. Taking more once you're already sufficient doesn't add benefit — this is about topping up a shortfall, not stacking.

CAUTIONS
  • !Fat-soluble, so more is not better — very high long-term doses can be harmful.
  • !A blood test (25-hydroxyvitamin D) removes the guesswork; ask your doctor.

Note:General information, not medical advice. Supplements interact with medications and conditions — check with your doctor before starting anything, especially if you're pregnant, nursing or managing a health condition.

Not sure what you actually need?

BOOK YOUR ASSESSMENT →