Vitamin D Deficiency: Who Needs Testing and Who Needs Supplements
Few tests are ordered as often, or as unnecessarily, as vitamin D. The paradox is real: deficiency is common across Indian populations despite abundant sunlight, and at the same time large numbers of tests are done in people for whom the result will not change anything useful.
Why deficiency is common in a sunny country
- Skin pigmentation reduces vitamin D synthesis; more melanin means longer sun exposure is needed for the same production
- Urban lifestyles keep people indoors during peak UVB hours
- Air pollution in major cities filters UVB
- Clothing that covers most skin
- Widespread and appropriate use of sunscreen
- Very few naturally vitamin D-rich foods in a typical Indian diet, and limited fortification
- Higher body fat sequesters vitamin D, so requirements are greater with obesity
What vitamin D actually does
Its established role is calcium absorption and bone mineralisation. Severe deficiency causes rickets in children and osteomalacia in adults, which are real bone diseases with bone pain, muscle weakness and fractures.
The wider claims are weaker. Large randomised trials of vitamin D supplementation in people who are not deficient have generally failed to show reductions in cancer, cardiovascular events, diabetes or depression. Observational studies keep finding associations, but low vitamin D is often a marker of poor health rather than its cause: people who are ill, inactive and indoors have lower levels.
This is worth knowing, because it sets expectations. Correcting genuine deficiency helps bone and muscle health. Taking supplements on top of a normal level does not appear to deliver the broader benefits often claimed.
What the numbers mean
Measured as serum 25-hydroxyvitamin D, in ng/mL:
- Below 10: severe deficiency, associated with bone disease
- 10-20: deficiency
- 20-30: insufficiency
- 30-60: generally considered sufficient
- Above 100: risk of toxicity with sustained high intake
Who should actually be tested
Testing makes sense when a result would change management:
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- Bone pain, proximal muscle weakness or unexplained fractures
- Osteoporosis or osteomalacia
- Malabsorption – coeliac disease, inflammatory bowel disease, after bariatric surgery
- Chronic kidney or liver disease
- Long-term steroid, anticonvulsant or antiretroviral therapy
- Elderly or housebound people, and residents of care facilities
- Infants and children with growth faltering or bowing of the legs
Routine testing in a healthy, asymptomatic adult is rarely useful. Where deficiency is likely on lifestyle grounds, taking a modest daily supplement is cheaper than the test.
Sensible supplementation
- Maintenance for most adults: 1000-2000 IU daily, or 60,000 IU once a month
- Correcting documented deficiency: commonly 60,000 IU weekly for six to eight weeks, then a maintenance dose
- Pregnancy and lactation: supplementation is generally recommended; follow obstetric advice
- Infants: 400 IU daily is recommended for breastfed babies in most guidelines
Vitamin D3 (cholecalciferol) is preferred over D2. Because it is fat-soluble, taking it with a meal containing some fat improves absorption.
Calcium intake matters alongside it – vitamin D cannot mineralise bone without adequate calcium from dairy, ragi, sesame, green leafy vegetables or supplements where diet falls short.
Doses to avoid
Very high intermittent doses, such as 300,000 IU or more in a single injection or drink, have been associated with increased falls and fractures in trials, and offer no advantage. Sustained intake above roughly 4000 IU daily without monitoring risks hypercalcaemia, with nausea, excessive thirst, kidney stones and, over time, kidney damage.
Sunlight in practice
For most people with moderate skin pigmentation, roughly 20-30 minutes of midday sun on the arms and face several times a week supports adequate production, with longer needed for darker skin. This has to be balanced against skin cancer risk and heat exposure, and it is unreliable in winter, in heavily polluted cities and for anyone mostly indoors, which is why supplementation is often the more practical route.
When to see a doctor
- Persistent bone pain, particularly in the ribs, hips, pelvis or thighs
- Difficulty rising from a chair or climbing stairs due to weakness
- A fracture from a minor fall
- A child with delayed walking, bowed legs or a widened wrist
- Symptoms of high calcium while on supplements: nausea, constipation, excessive thirst, confusion
This article is general health information. Do not take high-dose vitamin D long term without medical supervision and periodic monitoring.