Why Vitamin D Matters
Vitamin D helps your body absorb calcium and supports bone health, muscle function, and immune health. Low vitamin D is common, especially in people who spend most of their time indoors, live in northern climates, have darker skin, or carry excess weight.
How Vitamin D Is Measured
The standard blood test measures 25-hydroxyvitamin D, usually reported in ng/mL (or nmol/L outside the U.S.).
What Level Should You Aim For?
Expert groups don't fully agree, but general guidance looks like this:
- Below 12 ng/mL: Deficient
- 12–20 ng/mL: Insufficient for some people
- 20 ng/mL or higher: Considered adequate for bone health by the National Academy of Medicine
- 30 ng/mL or higher: A target some clinicians and organizations prefer, especially for people with bone or other health concerns
- Above 100 ng/mL: Risk of toxicity
Many clinicians aim for a range of roughly 30–50 ng/mL. More is not necessarily better, and very high levels can be harmful.
How Much Should You Supplement?
The right dose depends on your starting level, body weight, sun exposure, and health conditions.
- The recommended daily intake for most adults is 600–800 IU
- People with low levels often need more—commonly 1,000–2,000 IU daily, and sometimes higher under medical supervision to correct a deficiency
- The upper limit for most adults without medical supervision is 4,000 IU per day
Vitamin D3 (cholecalciferol) is generally preferred. Taking it with a meal that contains fat may improve absorption.
Why Test First?
Taking high doses without knowing your level can lead to excess calcium in the blood, kidney stones, and other problems. Testing lets you:
- Know whether you need to supplement at all
- Choose the right dose
- Recheck after about three months to see if your level has improved
Food and Sun Sources
- Fatty fish like salmon, trout, and sardines
- Egg yolks
- Fortified milk, plant milks, and cereals
- Sensible sun exposure (balanced against skin cancer risk)
Learn more about lab testing here: Heva Lab Testing
The Bottom Line
Most people do well with a vitamin D level of at least 20–30 ng/mL, with many clinicians targeting 30–50. Test before supplementing, choose a dose based on your results, and recheck to stay in a healthy range.