BLOOD TEST · SMART CARE POLYCLINIC, DEIRA
Vitamin B12 explained
A vitamin the body cannot make, needed for nerves and for producing red blood cells.
What the Vitamin B12 test measures
B12 comes only from animal foods or supplements. The body needs it to make red blood cells and to maintain the sheath around nerves, and it is stored in the liver in amounts that take years to run down. A single serum B12 level is an imperfect test — results near the lower end can be misleading in both directions, and the haematology guideline sets out when further testing is needed.1
What the result tells you
It causes large-cell anaemia
Which is why an unusually large red cell size on a blood count leads straight to this test.
The nerve effects are why it is corrected
Pins and needles, numbness in hands or feet, poor balance, memory and concentration problems. Prolonged deficiency can cause permanent nerve damage.
The cause decides the treatment
Diet, long-term metformin or acid-reducing medication, or reduced absorption from the stomach — which is what decides whether tablets are enough or injections are needed.
How to prepare
- Fasting
- Not needed
- Best time
- Any time of day
- Worth knowing
- Tell the nurse if you take B12 supplements or have had an injection recently — either raises the result and can hide a deficiency.
What can move the result
A result outside the usual range does not on its own mean something is wrong. These are the everyday explanations a doctor considers first.
Packages that include it
Frequently asked questions
B12 comes only from animal foods or supplements. The body needs it to make red blood cells and to maintain the sheath around nerves, and it is stored in the liver in amounts that take years to run down. A single serum B12 level is an imperfect test — results near the lower end can be misleading in both directions, and the haematology guideline sets out when further testing is needed. It causes large-cell anaemia: Which is why an unusually large red cell size on a blood count leads straight to this test.
Fasting: Not needed. Best time: Any time of day. Tell the nurse if you take B12 supplements or have had an injection recently — either raises the result and can hide a deficiency.
Commonly: a vegetarian or vegan diet; metformin taken long term; long-term acid-reducing medicines; conditions affecting stomach or bowel absorption; age, as absorption falls in later life. A single result is not a diagnosis. Values are read against the laboratory's own reference range and alongside your history, your symptoms and the rest of the panel — which is why every package includes a doctor to go through them with you.
At Smart Care Polyclinic, 29 Doha Centre, Al Maktoum Rd, Deira, Dubai. It is included in the Smart Total Health 360°, the Smart Extra Health, the Fatigue Panel, the Hair Loss Panel, the Essential Vitamins, the Stress Burnout, or it can be ordered on its own. Walk in during opening hours or call +971 (0)4 379 3562.
Sources
Written from current guidance and reviewed 31 August 2026.
Sources cited above
- Devalia V, Hamilton MS, Molloy AM, British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. British Journal of Haematology. 2014;166(4):496-513. PMID 24942828. doi:10.1111/bjh.12959The British Committee for Standards in Haematology guideline on diagnosing vitamin B12 deficiency, including the limits of a single serum B12 level.
Sources are listed for the specific statements they support. They are published research and guidance, not a substitute for a consultation — what applies to you is decided by a doctor who has assessed you.
- Vitamin B12 testMedlinePlus, US National Library of Medicine
- Vitamin B12 or folate deficiency anaemiaNHS
- Vitamin B12 and folateTesting.com, Association for Diagnostics & Laboratory Medicine