Vitamin D deficiency: symptoms, testing, and simple fixes
Feeling tired, getting more colds than usual, or noticing weak bones? Low vitamin D can cause vague but real problems. This page explains how to spot deficiency, what the blood test tells you, and clear steps you can take right away.
How to check and understand your levels
The right blood test is 25-hydroxyvitamin D (25[OH]D). Values under 20 ng/mL (50 nmol/L) usually mean deficiency; 20–30 ng/mL is low; many doctors aim for 30–50 ng/mL for general health. Ask for this test if you have bone pain, muscle weakness, frequent infections, fatigue, or risk factors like older age, darker skin, obesity, little sun exposure, or gastrointestinal conditions that cause poor absorption.
Testing is quick. If your level is low, your clinician will choose a treatment plan based on how low it is and your health history. Don’t guess doses on your own — both under-treating and over-treating have downsides.
Practical steps to raise your vitamin D
Sun exposure helps your skin make vitamin D. Short, regular sun sessions work best: about 10–30 minutes of midday sun on arms and legs a few times per week, depending on skin tone, season, and where you live. Sunscreen, cloud cover, and northern or southern latitudes limit production, so sun alone may not be enough year-round.
Eat vitamin D-rich foods: oily fish (salmon, mackerel, sardines), fortified milk and plant milks, fortified cereals, and egg yolks. Food usually helps maintain levels but rarely fixes a deficiency by itself.
Supplements are the most reliable fix. Vitamin D3 (cholecalciferol) raises blood levels better than D2. Typical approaches: for mild low levels, 1,000–2,000 IU daily; for clear deficiency some clinicians use 50,000 IU once weekly for 6–8 weeks, followed by a maintenance dose. Older adults often need at least 800–1,000 IU daily. People with obesity or after weight-loss surgery may need higher doses—talk to your doctor.
Watch for drug and health interactions. Certain medicines (some anticonvulsants, long-term steroids) and conditions (malabsorption, chronic kidney disease) change vitamin D needs. Too much vitamin D can cause high calcium, nausea, and kidney problems, so follow testing and medical advice when using high doses.
Retest blood levels 8–12 weeks after starting treatment to check progress. If levels reach your target, switch to a maintenance plan and retest periodically. If you have osteoporosis, autoimmune disease, or other chronic conditions, discuss long-term monitoring with your clinician.
Want a practical next step? Ask your GP or local clinic for a 25(OH)D test. Small changes—a short walk in the sun, two oily fish meals a week, and a daily supplement if needed—can improve energy, immunity, and bone health. If you’re unsure about dosing or have other health issues, get medical advice before changing supplements.
