Also seen on reports as: 25(OH)D, 25-OH Vitamin D, Calcidiol, Vitamin D Total
What is Vitamin D?
Vitamin D is essential for absorbing calcium and phosphorus from food and for keeping bones, muscles, and the immune system working well. The body makes Vitamin D in the skin when ultraviolet B (UVB) rays from sunlight hit it; smaller amounts come from foods like fatty fish, egg yolks, and fortified milk.
The standard blood test is 25-hydroxyvitamin D — usually written as 25(OH)D or simply 'Vitamin D' on Indian lab reports. This is the form the body stores and is the best single marker of overall Vitamin D status. The active form (1,25-dihydroxyvitamin D) is rarely tested in routine practice — it does not reflect stores reliably.
The test is run on a small blood sample drawn from a vein. NABL-accredited Indian labs typically report 25(OH)D in ng/mL; some report in nmol/L (conversion: ng/mL × 2.5 = nmol/L).
Why doctors order it
Vitamin D is one of the most ordered single-nutrient tests in India because deficiency is widespread — studies and ICMR-NIN guidance place prevalence of insufficiency or deficiency at roughly 70–90% of Indian adults across age groups, despite abundant sunshine in most of the country.
Doctors order it when symptoms suggest deficiency — diffuse bone or muscle pain, persistent tiredness, frequent falls, recurrent fractures from minor injuries, muscle weakness — and as a routine baseline in many adult health-check packages. It is also part of work-up for unexplained raised ALP (an alkaline phosphatase rise from bone osteomalacia), low calcium, and certain hair/skin/nail symptoms (though Vitamin D is not the cause of every such complaint).
It is routinely checked in pregnancy, breastfeeding, in children with growth concerns or suspected rickets, in elderly Indians, in people with limited sun exposure (housebound, indoor workers, traditional dress habits), in people with darker skin pigmentation (more melanin reduces UVB penetration), and in those on long-term steroid or anti-seizure medication. It is also followed up periodically when supplementation has been started.
What the result means
Most Indian and international guidelines (ICMR-NIN, Endocrine Society of India, Endocrine Society) use broadly similar categories — below 20 ng/mL is deficiency, 20–29 ng/mL is insufficiency, and 30–100 ng/mL is sufficient. Some Indian endocrinologists use stricter targets in symptomatic patients (aiming for >30 or even >40 ng/mL).
Severely low Vitamin D (typically below 10–12 ng/mL with raised ALP and low calcium) suggests osteomalacia in adults or rickets in children — a clinical condition that needs treatment. Levels above 100 ng/mL are uncommon, usually reflect over-supplementation, and can cause high calcium and other problems — supplementation should not be unmonitored at high doses.
A widespread misconception is that abundant sunshine guarantees adequate Vitamin D. In India this is not the case — indoor lifestyles, atmospheric pollution that filters UVB in many cities, darker skin pigmentation, traditional dress patterns, and sun-avoidance from heat all combine. So sun exposure alone is rarely enough for many Indian adults; dietary intake from vegetarian Indian diets is also typically limited.
Reference range
Values in ng/mL. To convert to nmol/L, multiply by 2.5.
- Deficient
- Below 20 ng/mL — typically warrants supplementation under medical guidance
- Insufficient
- 20 – 29 ng/mL — borderline; supplementation often recommended
- Sufficient
- 30 – 100 ng/mL — adequate for most healthy people
- Stricter target (symptomatic / specific situations)
- Some Indian guidelines target >30, or >40 ng/mL in selected patients
- Excessive / Toxicity risk
- Above 100 ng/mL — usually from over-supplementation; can cause high calcium
Vitamin D deficiency in Indian adults is widespread (~70–90% by published surveys) despite available sunshine. Treatment doses, frequency, and duration are individualised by the doctor — many Indian endocrinologists use weekly loading regimens followed by lower maintenance doses; self-supplementation at high doses without monitoring is not advised.
In India
What this test means for an Indian reader
Vitamin D deficiency affects an estimated 70–90% of Indian adults across age groups, despite abundant sunshine. Contributing factors include skin pigmentation, indoor lifestyles, air pollution that filters UVB, and traditional dress patterns that limit sun exposure. Deficiency is widespread enough that many Indian doctors test routinely in symptomatic patients.
ICMR-NIN and the Endocrine Society of India follow the broad international cutoffs — deficient <20 ng/mL, insufficient 20–29 ng/mL, sufficient ≥30 ng/mL — though some Indian endocrinologists use stricter thresholds for symptomatic patients.
Indian guidelines & references
- ICMR-NIN Vitamin D guidance
- Endocrine Society of India
- Indian Academy of Pediatrics (IAP) Vitamin D recommendations
Common factors that affect the result
Sun exposure is the dominant driver of Vitamin D in the body. Skin pigmentation (more melanin reduces UVB penetration), time spent outdoors at peak UVB hours (roughly 10am–3pm), surface area of skin exposed, sunscreen use, and atmospheric pollution all affect skin production. Northern Indian winters and high-pollution cities reduce effective UVB substantially.
Dietary intake is limited in most Indian diets. Fatty fish, fortified milk, egg yolks, and Vitamin-D-fortified cereals contribute the most. Pure vegetarian and vegan Indian diets without supplements are particularly limited. Some traditional Indian foods (ghee in modest amounts, mushrooms exposed to sunlight) provide small amounts.
Several conditions affect Vitamin D status — obesity (Vitamin D is sequestered in fat tissue and less bioavailable), chronic kidney disease (the kidney activates Vitamin D and disease reduces activation), liver disease, malabsorption (coeliac disease, inflammatory bowel disease, gastric bypass surgery), and certain medications (long-term steroids, some anti-seizure medications, rifampicin used for TB). Pregnancy and breastfeeding increase demand.
When to talk to your doctor
- Your Vitamin D is below 20 ng/mL — particularly if you have bone or muscle pain, weakness, or symptoms suggestive of osteomalacia.
- You have raised ALP (alkaline phosphatase) on liver function tests with normal liver enzymes — Vitamin D deficiency with osteomalacia is a common Indian cause that often goes unrecognised.
- You are pregnant, breastfeeding, post-menopausal, elderly, or have limited sun exposure — periodic Vitamin D monitoring is often recommended.
- Your child has bowing of legs, delayed growth, delayed walking, or other signs that could suggest rickets — paediatric evaluation is warranted.
- You are about to start or are already on high-dose Vitamin D supplementation — monitoring is important; very high levels can cause harm.
Related tests
Sources
- ICMR-NIN Vitamin D Guidance — Indian Council of Medical Research — National Institute of Nutrition
- Endocrine Society of India Vitamin D Position Statement — Endocrine Society of India
- Indian Academy of Pediatrics (IAP) — Vitamin D in Children — Indian Academy of Pediatrics
- AIIMS Endocrinology Vitamin D Protocols — All India Institute of Medical Sciences
- WHO Vitamin D Supplementation Guidance — World Health Organization
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