Shows how much vitamin D is in your blood to support bones, muscles, and immunity.
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Clinicians check vitamin D when you have risk factors or symptoms related to bone or muscle health. It helps guide supplement dosing and monitor your response over time. It’s useful if you get little sun, have darker skin, cover your skin, or have conditions that affect absorption. Testing is also common during pregnancy, in older adults, and for people with kidney or liver concerns.
Clinicians check vitamin D when you have risk factors or symptoms related to bone or muscle health. It helps guide supplement dosing and monitor your response over time. It’s useful if you get little sun, have darker skin, cover your skin, or have conditions that affect absorption. Testing is also common during pregnancy, in older adults, and for people with kidney or liver concerns.
High: Often from taking too much supplement; it can raise blood calcium. Review your dose with a clinician and avoid unnecessary high-dose products. Low: Common with limited sun, low intake, or absorption issues; it may relate to weaker bones or muscles. Discuss safe supplement options and sun habits, and consider a recheck after changes. Cutoffs vary by guideline; trends and your health context matter most.
Common factors include season and latitude, sunscreen use, and skin tone, which affect sun-made vitamin D. Recently taken high-dose supplements can shift values. Some medicines (such as anticonvulsants, glucocorticoids, or orlistat) may lower levels. High-dose biotin can interfere with some assays. Pregnancy, obesity, and acute illness can also change results. Try to use the same lab and method when tracking trends.
Special situations: if results don’t match your picture, confirm with LC-MS/MS and check calcium and parathyroid hormone; do not stop medicines without medical advice.
What does this test measure? It measures 25-hydroxyvitamin D, the main storage form of vitamin D in your blood.
Do I need to fast? No. You can eat and drink normally unless your clinician gives other instructions.
Should I stop supplements before testing? Avoid taking high-dose vitamin D or biotin right before the draw, unless your clinician advises otherwise.
What can affect my result? Season and sun exposure, skin tone, age, pregnancy, body weight, supplements, and some medicines can change levels.
How often should I test? If you start or change supplements, many people recheck after a few months. Once stable, test as your clinician recommends.
How long do results take? Most labs report results within one to three business days.
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