Vitamin D deficiency is common in India. That does not make every test necessary.

Vitamin D deficiency is genuinely common across India, including in sunny cities, and it is worth understanding why before deciding what to do about it.

Why deficiency is common despite the sunshine

Skin makes vitamin D from direct ultraviolet B exposure, and several things get in the way: darker skin pigmentation, which is protective against sun damage but slows synthesis; indoor working hours; air pollution, which absorbs UVB in the very cities where most people live; clothing that covers most of the skin; and sunscreen. Diet contributes little, because few Indian foods contain much vitamin D and fortification is limited.

What deficiency actually causes

Severe, prolonged deficiency causes osteomalacia — soft, painful bone, with muscle weakness, difficulty rising from a chair or climbing stairs, and a characteristic waddling gait. In children it causes rickets. It also contributes to osteoporosis, and it impairs calcium absorption, which matters a great deal for anyone with parathyroid disease.

Mild deficiency, however, is often blamed for things it does not cause. Generalised tiredness and diffuse body ache have many explanations, and a low vitamin D level found during their investigation is frequently incidental rather than causative. Correcting it is reasonable; expecting it to resolve all symptoms often is not.

Who should be tested

Testing is worthwhile where the result will change management: bone pain or proximal muscle weakness suggesting osteomalacia; osteoporosis or a low-trauma fracture; abnormal calcium, phosphate or alkaline phosphatase; chronic kidney or liver disease; malabsorption, coeliac disease or previous bariatric surgery; long-term steroid or anti-epileptic treatment; and pregnancy or infancy where clinically indicated.

For a healthy adult with no symptoms and no risk factors, routine screening is not established practice, and a sensible intake of vitamin D is a more proportionate response than a test.

A word about the big weekly doses

Sachets of 60,000 IU are dispensed extremely freely in India, often without a test before or after, and sometimes continued for months on end. Vitamin D is fat-soluble and accumulates. Excess can raise blood calcium, causing thirst, nausea, constipation, kidney stones and, at the extreme, kidney damage.

Correction of a genuine deficiency followed by an appropriate maintenance intake is the right pattern. Indefinite high-dose supplementation without monitoring is not, and it is particularly hazardous in anyone with hyperparathyroidism, sarcoidosis or kidney disease. Dose and duration should come from your own doctor and your own level, which is why no figures are given here.

Calcium and vitamin D are not interchangeable

Vitamin D helps the gut absorb calcium; it is not a substitute for having calcium to absorb. Milk, curd, paneer, ragi, sesame, small fish eaten with the bones and green leafy vegetables all contribute. Diet first, supplements where diet cannot manage it.

Sunlight, sensibly

Around fifteen to twenty minutes of midday sun on the arms and legs, several times a week, contributes usefully for most people with lighter skin and rather more is needed for darker skin. Through glass it does not work at all, since window glass blocks UVB.