By Karim Hammam
Consumer watchdog Which? has warned that rapid vitamin D tests sold for home use may return unreliable results, potentially deterring people from seeking help for a genuine deficiency.
Investigation finds significant variation
Which? compared five widely available rapid self-testing kits, each costing around £8, against a laboratory blood test from a Care Quality Commission-registered lab taken on the same day. The laboratory test showed vitamin D levels within the sufficient range, above 50 nmol/L. However, the rapid tests use a higher cutoff of 75 nmol/L to define sufficiency, meaning more people would be flagged as insufficient than by an NHS-ordered blood test.
In the study, only two of the five rapid tests indicated insufficient levels, while two others showed deficient levels markedly lower than the lab result. One test indicated a sufficient level. The contradictory outcomes could leave consumers unnecessarily worried, falsely reassured, or spending money on high-dose supplements they do not need.
Health risks from inaccurate results
The Royal College of Pathologists advises that excessive vitamin D intake over time can raise blood calcium levels, potentially leading to kidney stones. Conversely, untreated vitamin D deficiency can impair calcium absorption and increase the risk of osteoporosis. Vitamin D deficiency is common in the UK, partly due to insufficient sunlight during winter months.
Regulator reviewing standards
Which? shared its findings with the Medicines and Healthcare products Regulatory Agency (MHRA). The regulator confirmed it is reviewing existing regulations, with proposed changes aimed at raising standards for self-tests. None of the companies involved provided Which? with specific evidence supporting the accuracy claims on their packaging.
Experts urge professional advice
Which? head of consumer rights and food policy Sue Davies said inaccurate results risk driving people to take potentially harmful high-dose supplements or leaving a genuine deficiency untreated. The consumer body advises anyone concerned about their vitamin D levels to consult a qualified healthcare professional before relying on a rapid home test or starting supplements.
