Approximately 40% of US adults are vitamin D deficient. It affects bone density, immune function, mood, hormones, and muscle function — and most people don't know their level.
The Stack Analyzer maps your goals and current data to the right measurement path, protocol, and stack — in order.
The 25-hydroxyvitamin D test (25-OH vitamin D) measures the storage form of vitamin D in your blood — the best indicator of overall vitamin D status. Vitamin D3 (from sunlight, food, or supplements) is converted in the liver to 25-OH vitamin D, which is then activated by the kidneys as needed.
Most people in the modern world spend insufficient time in direct sunlight, and the limited food sources of vitamin D (fatty fish, egg yolks, fortified foods) rarely provide enough without supplementation. Above 37° latitude — roughly the northern US and most of Europe — meaningful vitamin D synthesis from sunlight is impossible from October through March regardless of outdoor exposure.[1]
ng/mL (nanograms per milliliter)
40–60 ng/mL
Under 30 ng/mL
Under 20 ng/mL
After 90 days of supplementation to confirm level correction
Reference ranges vary by lab, age, sex, medication status, and clinical context. Use these as discussion prompts with your clinician — not as diagnosis.
Form: D3 (cholecalciferol) only — not D2. D3 is the form produced by human skin from sunlight and is significantly more effective at raising serum levels.
With K2: Vitamin K2 (MK-7 form) ensures calcium is directed to bone rather than arteries. When supplementing D3 at higher doses, always pair with K2.
Dose: 2,000–5,000 IU/day is appropriate for most deficient adults. Retest after 90 days and adjust. Do not exceed 10,000 IU/day long-term without medical supervision.
With fat: Vitamin D is fat-soluble — take with a meal containing fat for best absorption.
The Stack Analyzer uses your measurements to build a personalized protocol, supplement stack, and 30-day plan.