What It Measures
This test measures the level of 25-hydroxyvitamin D in your blood, which is the main circulating form of vitamin D. It reflects your total vitamin D status from all sources — sunlight, food, and supplements — and is converted by the kidneys into the active hormone calcitriol (1,25-dihydroxyvitamin D) that regulates calcium, phosphorus, and immune function.
Vitamin D is a fat-soluble secosteroid hormone essential for calcium absorption, bone health, immune function, and mood regulation. The 25(OH)D blood test is the most reliable indicator of vitamin D status and reflects both dietary intake and sun exposure. Deficiency is extremely common worldwide and linked to a wide range of chronic diseases.
Current Value
What High Means
Elevated vitamin D levels (>100 ng/mL) indicate vitamin D toxicity (hypervitaminosis D), almost always caused by excessive supplementation rather than sun exposure or diet. Toxicity leads to hypercalcemia — dangerously high calcium levels — which can cause kidney damage, calcium deposits in soft tissues, kidney stones, nausea, and cardiac arrhythmias. Levels between 80-100 ng/mL are generally safe but offer no additional benefit over the 40-60 ng/mL range.
Possible Symptoms
Nausea, vomiting, poor appetite, constipation, excessive thirst, frequent urination, kidney stones, confusion, muscle weakness, bone pain, cardiac arrhythmias, weight loss, fatigue. Symptoms are primarily from resulting hypercalcemia rather than vitamin D itself.
What Low Means
Low vitamin D (<30 ng/mL) is associated with impaired calcium absorption, leading to weakened bones (osteoporosis, osteomalacia, rickets in children), increased fracture risk, and muscle weakness. Deficiency is also linked to increased susceptibility to infections, autoimmune diseases (multiple sclerosis, type 1 diabetes), depression, cardiovascular disease, and increased all-cause mortality. Severe deficiency (<20 ng/mL) significantly elevates risk for these conditions.
Possible Symptoms
Fatigue, muscle weakness, bone pain, frequent illness or infections, slow wound healing, depression, hair loss, muscle cramps, joint pain, difficulty thinking clearly, poor sleep quality, back pain, impaired recovery from exercise.
Risk Factors
Osteoporosis, osteomalacia, rickets, increased fracture risk, cardiovascular disease, type 2 diabetes, multiple sclerosis, rheumatoid arthritis, depression, seasonal affective disorder (SAD), increased infection susceptibility, certain cancers (colorectal, breast, prostate), all-cause mortality, cognitive decline, autoimmune conditions, metabolic syndrome.
Actionable Advice
Supplements
- •Vitamin D3 (cholecalciferol)
- •Vitamin K2 (MK-7, take with D3)
- •Magnesium glycinate (required cofactor)
- •Calcium (if dietary intake insufficient)
- •Cod liver oil
- •Vitamin D3+K2 combination supplements
Diet & Lifestyle
- •Get 10-30 minutes of midday sun exposure on arms and legs 2-3x per week (without sunscreen, adjusted for skin tone)
- •Supplement with D3 (not D2) — typical dose 2,000-5,000 IU/day depending on current levels
- •Always take vitamin D with a fat-containing meal for absorption
- •Co-supplement with vitamin K2 (100-200 mcg MK-7) to direct calcium to bones rather than arteries
- •Ensure adequate magnesium intake (400-600 mg/day) as it's required for vitamin D metabolism
- •Eat vitamin D-rich foods: fatty fish (salmon, sardines, mackerel), egg yolks, mushrooms exposed to UV light
- •Test levels every 3-6 months when optimizing, then annually once stable
- •Higher doses may be needed for obesity, malabsorption, darker skin tones, or northern latitudes
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Historical Trend
Related Biomarkers
Resources & Studies
All Readings
| Date | Value | Change |
|---|---|---|
| 2026-01-28 | 74 ng/mL | +4.0 |
| 2025-09-18 | 70.05 ng/mL | -4.0 |
| 2025-08-25 | 74 ng/mL | +53.3 |
| 2025-06-27 | 20.75 ng/mL | — |