India gets more sun than almost anywhere people live, and vitamin D is the one nutrient you can make yourself, from sunlight, for nothing. Yet large Indian surveys keep finding a big share of the people tested below the usual cut-off, in some city studies well over half. On one Indian forum thread, a Delhi reader posted a level of 11 and added that his doctor was not even surprised.
The sun has to reach your skin
Your skin makes vitamin D when one slice of sunlight, UVB, lands on it. UVB is fussy. It is strongest when the sun is high, late morning to early afternoon. It does not pass through window glass or get far through a haze of smoke and dust. It is stopped by sunscreen, and by cloth.
Now look at a weekday. You leave home at eight, when the UVB is weak. You spend the good hours, eleven to three, under a ceiling, beside a window that lets the heat through and stops the UVB at the glass. You come home after dark. The sunniest country in the world, and your skin saw twenty minutes of it, early, through a sleeve. As one commenter on that thread put it, going out in the sun is very tough.
Clothing, city air, and skin
Clothing. A kurta, a full-sleeve shirt, a sari that covers the arms. Most Indian clothing covers most Indian skin, sensibly, and the sun reaches the face and hands and not much else.
Air. In the big cities the air itself is a filter. Particles scatter UVB before it reaches the ground, and a bright winter sky on a bad-air day delivers little your skin can use.
Skin tone. Melanin is a natural sunscreen. Darker skin, which most of us have, needs longer in the sun to make the same amount of vitamin D. Often several times longer.
Food does not rescue it. Vitamin D is in oily fish, egg yolks and little else. Dal, roti, rice and sabzi carry almost none. Fortified milk and oil, the packs with the +F mark, carry a little, but a day's worth is a lot of milk.
IU and mcg are the same thing in two languages
IU stands for international units. Mcg is micrograms, a millionth of a gram. For vitamin D the conversion is fixed: 1 mcg is 40 IU. So 10 mcg is 400 IU, 15 mcg is 600 IU, 25 mcg is 1,000 IU, 50 mcg is 2,000 IU.
A label that says 15 mcg and one that says 600 IU are saying the same thing. Newer labels lean towards mcg and most doctors still speak in IU, so carry the one rule in your head: divide IU by 40.
What a sensible amount looks like
The Indian reference is the ICMR-NIN recommended dietary allowance of 2020: 600 IU a day for adults, which is 15 mcg. The average requirement is 400 IU; the RDA is set to cover nearly everyone. The dietary guidelines add roughly thirty minutes of sun, ideally between eleven and two. The tolerable upper limit, from all sources, is 4,000 IU a day.
Under FSSAI rules a health supplement may not carry more than one RDA of any nutrient, so a compliant Indian label shows at most 600 IU of vitamin D and a percent RDA of 100. That is the number to look for, and it is enough to keep a normal level normal in an adult who is not already short.
The 1,000, 2,000 and 5,000 IU tablets, and the 60,000 IU weekly sachet stirred into milk, are pharmacy medicines in India, sold under drug rules on a doctor's advice. Doctors prescribe them as a short course when a test shows someone is clearly low, and test again afterwards. It is a treatment plan, not a supplement. Do not buy it because a neighbour did.
The test is called 25-hydroxy vitamin D. It costs roughly one to two thousand rupees at a city lab, and is the only way to know your number.
D3, with K2, and how to read the pair
D2, ergocalciferol, comes from plants and fungi. D3, cholecalciferol, is the form your skin makes and it holds blood levels better, so it is the one to look for. Most D3 comes from lanolin, the grease in sheep's wool, and the FSSAI schedule lists D3 as animal-sourced. A brand claiming lichen D3, the vegetarian source, should be able to show its supplier's papers.
Vitamin D helps your body absorb calcium. Vitamin K2 helps direct that calcium to the bones, which is why the two are sold together. K2 comes in two common forms. MK-4 leaves the blood within hours. MK-7 stays for days, and it is the form most of the research used.
Read the pair like this. One line should say vitamin D3, as cholecalciferol, 600 IU or 15 mcg, ideally both, 100 percent RDA. The next should say vitamin K2, as MK-7, with its own amount in mcg. The Indian recommendation for vitamin K is 55 mcg a day, so 55 mcg is the most a compliant supplement can carry: less than many studies used, and what the rule allows. If the label says "vitamin K" with no form, or "K2" with no number, assume the cheaper form and a sprinkle. Both are fat-soluble, so take them with food.
In India the pair runs from roughly 4 rupees a day for a plain tablet to roughly 20 for a melt-on-the-tongue strip, often at the same 600 IU. Pay for the form and the report, not the format.
One caution. If you take a blood-thinning medicine, vitamin K interacts with it. Ask your doctor before you add K2.
What to expect
Nothing, for a while. A blood level takes roughly two to three months to settle. You will not feel a capsule of D3. Take 600 IU a day with food, get outside at lunch when you can, and let a repeat test after three months tell you where you are. It is slow and boring, and that is how it works.
What to check on your label
- The form: D3, cholecalciferol, not just "vitamin D".
- The amount in mcg or IU, ideally both: 15 mcg is 600 IU.
- Percent RDA against ICMR-NIN 2020, at or under 100 percent on a health supplement.
- The K2 form, MK-7, with its own amount, up to 55 mcg.
- The source, lanolin or lichen, if the green dot matters to you.
- A carrier oil in the other-ingredients line.
- The lot number and best-by date printed on the bottle itself.
Then read ours the same way: see the label
