Vitamin D

What is vitamin D?

Vitamin D is a fat-soluble vitamin that supports bone health, immunity, and hormonal function. Many people are insufficient, especially in low-sun environments, making supplementation common.

How does it work?

Vitamin D regulates calcium metabolism for bone integrity and plays roles in immune modulation and muscle function. Deficiency can impair performance, recovery, and overall health. Since food sources are limited, sun exposure or supplements are primary ways to maintain adequate levels. Pairing vitamin D with dietary Fats improves absorption. Indoor workers, darker skin tones, higher latitudes, winter months, and consistent sunscreen use all raise deficiency risk, making testing more important in these groups.

Practical application

Test serum 25(OH)D to personalize dosing. Common maintenance is 1,000-2,000 IU/day with a meal containing fat; higher corrective doses should follow medical guidance. Combine with magnesium and vitamin K2-rich foods (e.g., eggs, fermented foods) as part of a balanced diet. Re-test after 8-12 weeks if changing dose. Avoid excessive dosing to prevent hypercalcemia. Keep supplements stored away from heat and light to preserve potency, and log intake alongside other fat-soluble vitamins to avoid stacking unnecessary doses.

• BaselineGet 25(OH)D tested to set dosing; adjust with clinician input if needed.
• Dose & timingTake 1,000-2,000 IU/day with a fat-containing meal for absorption.
• SafetyRe-test after 8-12 weeks when changing dose; avoid unsupervised high-dose use.

Common mistakes

• Supplementing blindly without testing, risking under- or over-shooting.
• Taking vitamin D without dietary fat, reducing absorption.
• Using very high doses long term without monitoring calcium status.