Private Vitamin B12 (Active) Blood Test in the City of London

Vitamin B12 is an essential nutrient that plays a key role in red blood cell production, nerve function, and DNA synthesis. The body cannot produce B12 on its own, so it must be obtained through diet or supplementation.

B12 deficiency is relatively common, particularly among older adults, those following a vegan or vegetarian diet, and individuals with conditions affecting nutrient absorption. Symptoms can develop gradually and may be overlooked if not specifically tested.

What the Vitamin B12 (Active) (Venous) Measures

• Serum vitamin B12 levels — the total amount of B12 circulating in the blood
• Some profiles also include active B12 (holotranscobalamin) for a more specific assessment

When This Test May Be Helpful

• Persistent tiredness or fatigue
• Tingling or numbness in the hands or feet
• Difficulty concentrating or memory problems
• Mood changes, including low mood
• A vegan or vegetarian diet
• Digestive conditions that may affect absorption (e.g. coeliac disease, Crohn's disease)
• Use of certain medications such as metformin or proton pump inhibitors

Understanding Your Results

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

B12 levels are reported in picograms per millilitre (pg/mL) or picomoles per litre (pmol/L). Values below the laboratory reference range may indicate a deficiency, though symptoms and clinical context are also important.

If your results are low or borderline, your GP can advise on further investigation and supplementation. Untreated B12 deficiency can lead to neurological complications, so early identification is important.