Vitamin D test at home – 25-OH vitamin D from capillary blood

The test measures 25-OH vitamin D (calcidiol), the storage form of vitamin D in the blood. It is regarded as the usual marker of vitamin D status (PubMed 29141976, PubMed 21646368). A low value shows that little stored vitamin D is present in the blood.

Low values are common in Germany: in the nationwide DEGS1 study by the Robert Koch Institute, 61.6% of adults were below 50 nmol/l and 30.2% below 30 nmol/l; values were clearly lower in winter than in summer (PubMed 26162848). Long-lasting, severe deficiency can lead to rickets in children and to softening of the bones (osteomalacia) in adults (PubMed 17634462, PubMed 26745253). Professional societies define the threshold for "deficiency" differently; the report states the reference range of the laboratory that carried out the analysis.

Vitamin D toxicity is rare. It usually results from long-term intake of very high-dose supplements and causes complaints through a raised calcium level (hypercalcaemia). The symptoms described most often are confusion, apathy, repeated vomiting, abdominal pain, frequent urination, strong thirst and dehydration. 25-OH vitamin D values above 375 nmol/l (150 ng/ml) are typical of overdosing (PubMed 30294301).

A value above the laboratory's reference range should be assessed by a doctor, especially if you take vitamin D supplements or have any of these complaints.

The liver converts vitamin D into 25-OH vitamin D (calcidiol), the storage form in the blood. The active form, 1,25-dihydroxyvitamin D (calcitriol), is produced mainly in the kidney and is not suitable for assessing vitamin D status (PubMed 17634462).

The value is given in two units: 1 ng/ml corresponds to 2.5 nmol/l. Your report states the value in nmol/l. When comparing values from different laboratories, check the unit – otherwise identical values look very different.

Vitamin D controls how much calcium the gut absorbs from food. If vitamin D is lacking, less calcium is absorbed; the body compensates via parathyroid hormone and draws calcium from the bones. In the long run this can weaken the bones (PubMed 17634462).

With overdosing it is the other way round: too much vitamin D can raise the calcium level in the blood. This test measures only 25-OH vitamin D, not calcium or parathyroid hormone.

Most vitamin D is produced in the skin when UVB radiation from the sun reaches it. Only a few foods contain notable amounts, such as oily fish. Strictly speaking, vitamin D is more of a hormone precursor: the body converts it into its active form in several steps (PubMed 17634462).

Its role for calcium balance, bones and muscles is best established. Vitamin D receptors are also found in many other tissues, for example in immune cells; what this means for health is still being researched (PubMed 38828931).

In Germany, UVB radiation from about October to March is barely sufficient for the skin to produce vitamin D. In the DEGS1 study, lower values were associated with, among other things, examination in winter, living in the north, little exercise, a higher body mass index and not taking vitamin D supplements (PubMed 26162848).

Other known influences are older age, dark skin, little time outdoors, covering clothing, conditions in which fat is poorly absorbed, and some medications (PubMed 17634462, PubMed 21646368).

With this test you collect capillary blood from your fingertip at home and fill a CapiSave tube up to the 600 µl mark. The partner laboratory determines 25-OH vitamin D with an immunoassay (ELISA/CLIA) – the same marker that is measured from venous blood at a doctor's practice.

Measurement methods differ between laboratories, which is why work is ongoing to standardise 25-OH vitamin D measurement (PubMed 29141976). For comparisons over time it helps if values come from the same laboratory. Careful sampling matters: squeezing or residual alcohol on the finger can distort the sample.

In 2011, the Endocrine Society recommended measuring 25-OH vitamin D in people at increased risk of deficiency, but saw insufficient grounds for screening people without risk (PubMed 21646368). In its 2024 guideline it advises against routine testing in the general population, because studies showed no benefit of such screening and an optimal target level for disease prevention could not be defined (PubMed 38828931).

A test can still be a basis for a conversation, for example if there is a risk or you want to know your value while taking a supplement. Whether a measurement makes sense for you can be clarified with the ORY expert team or with your doctor or naturopath, for example from the ORY expert network.

Vitamin D levels vary with the seasons: they are usually higher after summer and lower after winter (PubMed 26162848). A single value is therefore a snapshot. If you want to compare values over time, it is best to measure at the same time of year and in the same laboratory.

The time of day does not matter for 25-OH vitamin D, and you do not need to fast.

Research associates vitamin D deficiency with the following complaints and conditions, with varying strength of evidence:

• Bone pain and muscle weakness due to softening of the bones (osteomalacia) in pronounced, long-lasting deficiency: well documented (PubMed 17634462).
• Rickets in children with bone deformities and impaired growth: well documented (PubMed 26745253).
• Lower bone density and a higher risk of fractures, especially in older age: observed in studies (PubMed 17634462).
• More frequent respiratory infections: in an analysis of individual data from trials, acute respiratory infections occurred somewhat less often with vitamin D, more clearly with very low baseline levels (PubMed 28202713).
• Fatigue, mood, cardiovascular health and metabolism: associations with low values have been described, but a cause-and-effect relationship has not been shown for many of them – under discussion (PubMed 38828931).

These are associations from studies and textbook knowledge, not causes in an individual person. A blood test cannot explain complaints and does not provide a diagnosis. Persistent complaints should first be assessed by a doctor.

With persistent bone or muscle pain, increasing muscle weakness, fractures without an adequate accident, or in children with bowed legs, growth problems or delayed development, the first step is a doctor's or paediatrician's practice, not a self-test.

Vomiting, strong thirst, very frequent urination or confusion should be checked by a doctor immediately, especially if you take high-dose vitamin D supplements. With kidney, liver or bowel diseases, after gastrointestinal surgery, during pregnancy and with medication that affects bone metabolism, the question of vitamin D belongs in medical care.

This page does not recommend supplements, diets or therapies. Whether a value means anything at all and which steps make sense depends on your overall situation: complaints, previous illnesses, medication and diet. Too much vitamin D can also be harmful (PubMed 30294301); supplements and doses therefore belong in professional guidance.

What makes sense for you belongs in a conversation with the ORY expert team or with your doctor or naturopath, for example from the ORY expert network. The results consultation is included in the price.

You do not need to fast. Drink enough water beforehand and warm your hands well, for example under warm water or by rubbing them. Clean your middle or ring finger with the alcohol swab and let the alcohol dry completely. Prick the side of the fingertip, wipe away the first drop of blood and fill the CapiSave tube up to the 600 µl mark without squeezing the finger.

If you take vitamin D supplements, you can still do the test; state your intake on the request form. Do not store the sample in heat or sunlight, and send it only from Monday to Thursday, not before public holidays.

Analysis usually takes 7–21 days from the arrival of the sample at the laboratory. As soon as your report is ready, we let you know. A results consultation with the ORY expert team is included in the price.

The vitamin D3 test costs €39.90 including VAT, shipping, return postage and results consultation.

Statutory health insurance in Germany generally does not cover a vitamin D test you order yourself. Whether there is a medical reason for a covered measurement in your case is something your doctor's practice can clarify. With private insurance, reimbursement may be possible; how it works is described under "Reimbursement by private insurance".

The vitamin D3 test (€39.90) measures only 25-OH vitamin D. The basic vitamin check (€98.50) also measures vitamin B12, folic acid, vitamin E and coenzyme Q10; for children from about 3 years there is the vitamin check for children & adolescents (€106.50). The OM Vital blood test (€205) combines vitamins with blood lipids, liver and kidney values, hs-CRP and TSH. For minerals there is the whole blood mineral analysis (€75).

Which scope makes sense for you can be clarified in the free initial consultation.