Vitamin B12

Critical for nerve function, DNA synthesis, and red blood cell production.

What it is

Vitamin B12 (cobalamin) is essential for neurological function, DNA repair, and the formation of red blood cells. It is only found naturally in animal products, making deficiency common in those eating little meat or taking certain medications.

Why it matters

Chemotherapy and some cancer medications can deplete B12 or impair its absorption. Deficiency causes fatigue, neuropathy (nerve damage), and megaloblastic anaemia — symptoms that can easily be misattributed to treatment side effects. Checking B12 is a simple fix for potentially correctable symptoms.

How to test

Standard blood test. No fasting required. Active B12 (holotranscobalamin) is more sensitive if available.

This information is for educational purposes only. Always discuss testing and interpretation of results with your care team.

Optimal range

Below 150 pmol/L

deficient — supplement or investigate absorption

150–300 pmol/L

low-normal, consider supplementing

Above 300 pmol/L

sufficient

How often

Every 6 months.