Vitamin D (25-Hydroxyvitamin D): What It Is and What Your Results Mean
Bottom line: Vitamin D is essential for bones, immunity, and mood. 30-50 ng/mL is optimal. Deficiency is extremely common, especially in northern climates.
What Is Vitamin D (25-Hydroxyvitamin D)?
Vitamin D is a fat-soluble vitamin that functions as a hormone in the body. It is essential for calcium absorption, bone health, immune function, and mood regulation. Your body produces vitamin D when your skin is exposed to sunlight.
The blood test measures 25-hydroxyvitamin D, the main circulating form of vitamin D and the best indicator of your body's vitamin D status. Deficiency is extremely common, affecting an estimated 1 billion people worldwide, particularly those in northern latitudes, people with darker skin, and older adults.
Low vitamin D has been linked to increased risk of osteoporosis, certain cancers, autoimmune diseases, cardiovascular disease, and depression. Supplementation is often necessary, especially during winter months.
Vitamin D (25-Hydroxyvitamin D) Reference Ranges
| Classification | Range (ng/mL) |
|---|---|
| Severely Deficient | Below 10 |
| Deficient | 10 - 19 |
| Insufficient | 20 - 29 |
| Sufficient/Optimal | 30 - 60 |
| High-Normal | 61 - 80 |
| Excessive | 81 - 150 |
| Toxic | 151 - 400 |
What Affects Your Vitamin D (25-Hydroxyvitamin D) Levels?
- Sun exposure (latitude, season, skin color, sunscreen use)
- Dietary intake (fatty fish, fortified milk, eggs)
- Supplementation
- Body weight (vitamin D is stored in fat tissue)
- Age (skin produces less vitamin D with age)
- Kidney and liver function (needed for activation)
When to Get Tested
Testing is recommended if you have risk factors for deficiency: limited sun exposure, dark skin, obesity, malabsorption conditions, osteoporosis, or unexplained fatigue and bone pain. Routine screening is debated, but many doctors include it in annual bloodwork.
Look Up Your Vitamin D (25-Hydroxyvitamin D) Result
Select your value below to see a detailed breakdown of what it means:
Severely Deficient
Deficient
Insufficient
Sufficient/Optimal
High-Normal
Excessive
Read the Full Blood Test Guide
Frequently Asked Questions
30-50 ng/mL is considered sufficient and optimal by most medical authorities. Below 20 ng/mL is deficient. 20-29 ng/mL is insufficient. Above 80 ng/mL may be excessive.
The recommended daily allowance is 600-800 IU for most adults. However, if you are deficient, your doctor may prescribe 2,000-5,000 IU daily or a high-dose weekly supplement to bring levels up.
It depends on your latitude, skin color, and sun exposure. People living above the 37th parallel (roughly north of Atlanta or Los Angeles) often cannot produce enough vitamin D from sunlight alone during winter months.
