At-home vitamin D tests could be giving unreliable results and preventing consumers from seeking help for a genuine deficiency, a watchdog has warned.

Which? said it found significant variation across rapid self-testing kit results compared with a laboratory blood test.

Vitamin D deficiency is common in the UK, partly because of a lack of adequate sunlight during the winter months, although factors such as diet and age can also play a role.

The watchdog bought five widely available rapid vitamin D tests, all costing around £8.

Results from the same person were compared with a Care Quality Commission (CQC) registered laboratory test taken on the same day, which showed vitamin D levels within a sufficient range.

Anything higher than a reading of 50 nmol/L is generally considered a sufficient level of vitamin D.

Rapid tests use a higher cut off of 75 nmol/L as a sufficient level, meaning more people will be flagged as insufficient compared with an NHS-ordered blood test.

By this measure, the Which?…