Vitamin D Deficiency: Signs, Tests, and What To Do

Feeling tired, achy, or catching every cold? Low vitamin D could be a cause. Vitamin D helps bones, muscles, and immunity. Many people are low and don’t know it because early signs can be subtle.

Who is at risk? Older adults, people with dark skin, those who spend little time outdoors, anyone who wears covering clothing often, people with obesity, and people with digestive problems that affect absorption. Certain medicines like anticonvulsants and some weight-loss drugs can lower vitamin D too.

How to check and treat low vitamin D

The simple test is a 25‑hydroxy vitamin D blood test. Doctors usually call levels under 20 ng/mL deficient, 20–30 ng/mL insufficient, and 30–50 ng/mL adequate for most adults. If you’re low, treatment depends on how low your level is. A common approach is a short course of higher-dose vitamin D (for example, 50,000 IU once a week for 6–8 weeks) followed by a daily maintenance dose. Daily maintenance often ranges from 800 to 2,000 IU, but your provider may adjust that based on your blood test, age, body weight, and health conditions. Always check with a clinician before starting high-dose supplements.

While you wait for test results or treatment, watch for clear signs of deficiency: bone or lower‑back pain, muscle weakness, frequent infections, slow wound healing, and low mood. If you have unexplained fractures or severe symptoms, seek medical care quickly.

Sunlight, food, and supplement tips that work

Sun exposure triggers vitamin D production in your skin. About 10–30 minutes of midday sun several times a week can help, but this varies by skin tone, season, and location. Foods with vitamin D include fatty fish (salmon, mackerel), fortified dairy or plant milks, fortified cereals, and eggs. Most people don’t get enough from diet alone.

Pick supplements with vitamin D3 (cholecalciferol) — it raises blood levels better than D2. If you’re on multiple medications or have kidney or liver disease, talk to your doctor before adding a supplement. If you take vitamin D long term, get repeat blood tests after 3 months to make sure levels are in a safe range.

Certain groups need special care: pregnant and breastfeeding people, infants, and people with kidney or liver disease should have vitamin D managed by a clinician. High doses can cause too much calcium — symptoms include nausea, weakness, frequent urination, and confusion. Tests and follow-up help avoid that. If you take calcium supplements, mention that to your provider. Keeping a simple log of doses and test dates makes follow-up easy. Ask for clear target ranges from your doctor.

Want quick steps? 1) Get a 25‑OH vitamin D test. 2) If low, follow a prescribed repletion plan. 3) Use daily maintenance doses and recheck levels. 4) Add safe sun exposure and vitamin‑D rich foods.

Read related articles on PharmaExpressRx.com for deeper info on supplements, obesity and vitamin absorption, and sleep health. If you have specific health conditions, ask your healthcare provider for tailored advice.