Vitamin D Test
Reviewed
Also called: 25-hydroxyvitamin D, 25(OH)D, cholecalciferol test, ergocalciferol test, calcidiol test, vitamin D2 test, vitamin D3 test
A vitamin D test measures the level of 25-hydroxyvitamin D (25(OH)D) in your blood to check if you have enough vitamin D for healthy bones, teeth, muscles, nerves, and immune system. It is used when your provider suspects a bone or other health condition related to very low vitamin D levels, or if you have risk factors for deficiency. Routine testing is not recommended for everyone.
Specimen: Blood
Why this test may be ordered
- To check for vitamin D deficiency if you have a condition such as osteomalacia, low bone density, osteoporosis, or rickets.
- If you have symptoms like bone pain, muscle weakness or aches, soft or deformed bones, or weak bones and fractures.
- If you have a high risk for deficiency due to limited sun exposure, poor diet, malnutrition, weight loss surgery, conditions that affect nutrient absorption (e.g., Crohn's disease, ulcerative colitis, celiac disease), kidney or liver disease, or certain medicines (e.g., statins, steroids, weight-loss medicines).
- For babies mainly fed breastmilk or children with diets low in vitamin D.
- To monitor if vitamin D levels are improving with supplements, or to check for toxicity if you have symptoms of too much vitamin D (nausea, vomiting, poor appetite, constipation, muscle weakness, weight loss).
Preparation and collection
You don't need any special preparations. Tell your provider about all medicines, vitamins, and supplements you take, because they may affect your results. Do not stop taking any medicines unless your provider tells you to.
Blood sample from a vein in your arm.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your test results may be reported as 'total vitamin D,' or as the amounts of vitamin D2 and vitamin D3. Total vitamin D is the important number to check. The results below describe total vitamin D levels.
- Deficient: Deficient Limitation: Very low vitamin D levels that are likely to affect your bones and general health. Next step: Prompt
- Insufficient: Insufficient Limitation: Low vitamin D levels that may weaken your bones and affect your health, even if you don't have symptoms. Next step: Prompt
- Sufficient or optimal: Sufficient or optimal Limitation: Vitamin D levels that are enough for good bone and general health for most people. Next step: Routine
- Toxic or possible toxicity: Toxic or possible toxicity Limitation: Very high vitamin D levels that might cause health problems. Usually means you're getting too much from supplements. Next step: Prompt
- There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
- Routine vitamin D testing is not recommended for everyone.
What to do next
To learn what your vitamin D test results mean, talk with your provider.
- Why is this test being ordered for me?
- What do my total vitamin D level and the result label (deficient, insufficient, sufficient/optimal, or toxic/possible toxicity) mean for my health?
- If my level is low, what are the recommended ways to increase it safely?
- If my level is high, what steps should I take to lower it?
- How often should I have this test repeated?