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Watchdog warns that home vitamin D tests vary widely

Which? found conflicting results when five rapid kits were compared with a laboratory blood test.

At-home vitamin D test kits can produce substantially different results from laboratory testing, consumer group Which? has warned. The findings have been shared with the Medicines and Healthcare products Regulatory Agency.

Which? bought five rapid vitamin D tests costing about £8 each and compared results from the same person with a laboratory test taken on the same day. The report said the laboratory result was within a range generally considered sufficient, while the rapid kits produced differing classifications.

Two of the home tests suggested an insufficient level, two indicated deficiency and one reported a sufficient result. Which? said the variation could leave consumers unnecessarily worried, falsely reassured or inclined to buy supplements they do not need.

The consumer group also highlighted a difference in thresholds. It said rapid tests used a threshold of 75 nanomoles per litre for sufficiency, while 50 nanomoles per litre is generally used as a sufficient level in the context of laboratory testing.

The investigation involved one person’s results and five products. It does not establish that every kit is inaccurate or that every consumer would receive the same pattern of results. Nor does it replace formal regulatory assessment of the products.

Vitamin D status can be affected by several factors, including diet, age and exposure to sunlight. The NHS and other health bodies use clinical context and appropriate testing when assessing possible deficiency; a consumer test result on its own does not establish what treatment a person needs.

Which? has urged the regulator to examine the products and the claims made about them. Consumers who are concerned about their health should use NHS or professional medical services rather than treating a single home test as a diagnosis.

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