Private Vitamin D (25-OH) Blood Test in the City of London

Vitamin D plays a central role in bone health, immune function, and muscle strength. It is produced naturally by the body when the skin is exposed to sunlight, and is also obtained through certain foods and supplements.

Vitamin D deficiency is widespread in the UK, particularly during autumn and winter months when sunlight exposure is limited. Public Health England has noted that a significant proportion of the UK population has low vitamin D levels, especially between October and March.

What the Vitamin D (25-OH) (Venous) Measures

• 25-hydroxyvitamin D — the main circulating form of vitamin D in the blood
• This is the standard laboratory marker used to assess vitamin D status

When This Test May Be Helpful

• Fatigue, tiredness, or general low energy
• Muscle weakness, aches, or bone pain
• Frequent infections or slow recovery from illness
• Limited sun exposure or living in the UK during winter months
• A diet low in vitamin D sources (e.g. oily fish, eggs, fortified foods)
• Dark skin, which reduces vitamin D production from sunlight
• Monitoring supplementation effectiveness

Understanding Your Results

Results are typically available within 1 day" and are delivered securely.

Vitamin D levels are measured in nanomoles per litre (nmol/L). Levels below 25 nmol/L are generally considered deficient, while levels between 25 and 50 nmol/L may be considered insufficient. Optimal levels are generally above 50 nmol/L, though reference ranges may vary between laboratories.

If your levels are low, supplementation is widely available and your GP can advise on the appropriate dose for your circumstances.