Low vitamin D

Clinically: Vitamin D deficiency · also low vitamin D, hypovitaminosis D

nutritional ICD-10 E55.9 MONDO MONDO:0100471 unverified

This describes what this condition typically looks like. It is not a diagnosis and cannot tell you whether you have it -- patterns overlap, results vary between labs, and the same numbers mean different things in different people. Diagnosis usually rests on 25-hydroxyvitamin D, interpreted alongside symptoms and history rather than read off a report.

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

Your body is short of vitamin D, which it needs mainly to absorb calcium and keep bone strong. Skin makes it from sunlight, so shortage follows the seasons.

Inadequate vitamin D status, assessed by serum 25-hydroxyvitamin D [25(OH)D], the best marker of status; deficiency is defined as 25(OH)D below 50 nmol/L (20 ng/mL) and severe deficiency as below 30 nmol/L (12 ng/mL). Because vitamin D is needed for intestinal calcium absorption, deficiency is associated with bone loss and fractures and can lead to osteoporosis or rickets.

caveats unverified

Vitamin D gets linked to a great many conditions in news coverage. Those links come from studies that watch people rather than test treatments, and when trials did test it, most benefits beyond bone health did not hold up.

No clinical version written yet.

How common it is

Very common, especially in winter, at higher latitudes, in people with darker skin, and in anyone who spends most of their time indoors.

The typical lab pattern

What the diagnosis rests on

The results a diagnosis is actually made on.

25-hydroxyvitamin D

low

ref 20–50

Vitamin D status is classified by blood 25-hydroxyvitamin D: deficiency is below 30 nmol/L (12 ng/mL), insufficiency 30 to 50 nmol/L.

Consistent with it

Fits the picture, but not enough on its own.

Calcium, total	low	—	Usually kept normal by parathyroid hormone; it falls in rickets or osteomalacia from long-standing deficiency.
Alkaline phosphatase	high	—	Raised once the deficiency affects bone (rickets or osteomalacia). Vitamin D deficiency is a common cause of an isolated raised ALP.
Phosphate	low	—	Falls as raised parathyroid hormone makes the kidneys lose phosphate; this is the step that leads to rickets or osteomalacia.

How it usually feels

Frequencies say how often a symptom accompanies this condition — not the other way round. Most people with any of these symptoms do not have this.