Vitamin D in a Baku winter

The skin makes most of our vitamin D itself under the sun’s UVB rays. Measurements in Boston (42° north) showed that from November to February the skin makes none, even on a cloudless day. Baku lies at 40°: at noon in December the sun rises only 26° above the horizon, and the picture here is much the same.

The store built up in summer runs down over winter, so we see the lowest results in February and March. It falls faster in people who work indoors, who wear clothes that cover the body, who are over 60 or who are overweight.

For vitamin D (25-⁠OH) there is no need to fast, and blood can be taken at any time of day. The result is ready at 18:00 on the next working day, and the test costs ₼45.

Our report gives a reference range of 30 to 100 ng/mL. Most doctors read a result below 20 ng/mL as a deficiency; your doctor judges anything between 20 and 30. Some laboratories report in nmol/L: 1 ng/mL is 2.5 nmol/L, so 30 ng/mL equals 75 nmol/L.

Your doctor sets the dose and how long to take it. Vitamin D dissolves in fat and builds up in the body: taking very high doses on your own for a long time can raise blood calcium. The laboratory does not diagnose or prescribe.

Repeat the test about 3 months into treatment, when the level has settled. Oily fish and egg yolks help, but in winter it is hard to cover the need with food alone.

Doctors often order ferritin, vitamin B12 and calcium with vitamin D. Vitamin D, ferritin, B12, folate, iron and a blood count come in one visit in the Vitamins and iron programme: ₼95.