What Is Vitamin D in a Blood Test?
Vitamin D testing measures 25-hydroxyvitamin D (25-OH D) — the storage form and best indicator of vitamin D status.
Reference Ranges
- Severe deficiency: below 12 ng/mL
- Deficiency: 12–20 ng/mL
- Insufficiency: 20–30 ng/mL
- Sufficient: 30–50 ng/mL
- Toxic: above 100 ng/mL
Why Vitamin D Matters
- Bone health — calcium absorption
- Immune function
- Muscle function
- Mood
- Cardiovascular health
Deficiency Causes
- Limited sun exposure
- Dark skin — melanin reduces synthesis
- Obesity
- Malabsorption — celiac, Crohn’s, gastric bypass
- Kidney/liver disease
- Age
- Medications — anticonvulsants
Supplementation
- RDA: 600–800 IU/day
- Deficiency treatment: 50,000 IU/week for 8 weeks
- Recheck level 8–12 weeks after starting
Source: NLM MedlinePlus, American Association for Clinical Chemistry.
Ratings summarize government-reported measures — they don't capture your personal needs. Visit the facility, ask about staffing and services, and use CMS checklists. This profile is informational only and is not a recommendation.
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