Watchdog warns of unreliable at-home vitamin D tests

The consumer watchdog Which? has warned that at-home vitamin D rapid testing kits may provide unreliable results. A study comparing five widely available kits, costing approximately £8 each, against a registered laboratory blood test revealed significant variations in accuracy.

While laboratory tests generally consider levels above 50 nmol/L as sufficient, rapid tests often use a higher threshold of 75 nmol/L. This discrepancy can lead to more individuals being flagged as insufficient. In the study, results ranged from sufficient to markedly deficient, even when the laboratory test indicated sufficient levels.

Inaccurate results pose several health risks. Consumers may experience unnecessary worry, feel falsely reassured, or consume high-dose supplements they do not require. The Royal College of Pathologists notes that excessive vitamin D intake can lead to high blood calcium levels and complications such as kidney stones.