Vitamin B12 (Active) Blood Test

Our active B12 test can tell you if you have a low level of vitamin B12 and whether you’re at risk of vitamin B12 deficiency anaemia, which affects the transport of oxygen around your body. 

Because around 70% of the vitamin B12 in your body is inactive, our test only measures your active vitamin B12 level, as this is thought to be the best early indicator of a deficiency. 

A vitamin B12 deficiency can cause a wide range of symptoms including extreme tiredness, a lack of energy, muscle weakness, pins and needles, and poor memory.

These symptoms usually develop gradually but can worsen if the condition goes untreated. It’s important that B12 deficiency anaemia is diagnosed and treated early, as other conditions and potential complications can develop alongside it over time.

Low vitamin B12 levels can be detected with a blood test, and in most cases, a deficiency can be easily reversed.

Vitamin B12 (cobalamin) is an essential water-soluble vitamin, found mostly in animal products, such as meat, fish, milk, and eggs. It’s used to make new cells and DNA (the genetic material in all your cells), and to keep your nerves and red blood cells healthy. 

We get vitamin B12 from our diet. So, if you don't eat enough vitamin B12-rich foods, you have a higher risk of a deficiency. You can also get a deficiency if your body is unable to absorb vitamin B12 properly, due to conditions such as coeliac disease or pernicious anaemia. 

Some of the most common causes of vitamin B12 deficiency include dietary insufficency, medications, poor absorption in the gut, and autoimmune gastritis (or pernicious anaemia). People who eat a diet low in dairy and animal products, such as people who eat a plant-based diet or have allergies, are at highed risk. Medications that increase your risk of vitamin B12 deficiency include colchicine, metformin, omeprazole, ranitidine, pregabalin, topiramate, and phenobarbital.

The recommended daily amount of vitamin B12 varies depending on your age. The table below gives the daily average vitamin B12 amount recommended at each life stage.

Age	Recommended amount (mcg)
1 year	0.5
2-3 years	0.5
4-6 years	0.8
7-10 years	1.0
11-14 years	1.2
15-18 years	1.5
19+ years	1.5

In some cases, making changes to your diet can improve your vitamin B12 level. Foods that are rich in vitamin B12 include meat, fish, eggs, and dairy products.

However, there are plant-based sources like yeast extract (such as Marmite) and fortified breakfast cereals. Find out more about plant-based diets and nutrition.

You may need to take a supplement to improve your level, and you should follow your GP’s advice carefully regarding treatments.

You can use our finger-prick B12 home test kit to check your level. This includes a full lab analysis of your blood sample and expert medical advice on any next steps. You can view your results and doctor’s comments on your MyMedichecks dashboard.

Measuring your total vitamin B12 might seem like the best way to check for a deficiency. However, only around 30% of the vitamin B12 in your body is available to use (known as active vitamin B12), while the rest is stored in an inactive form.

This means a normal total vitamin B12 result (including both active and inactive forms) could be misleading and may hide a deficiency. At Medichecks, we only measure your active vitamin B12 level to give you the most accurate result. You can find out more about the difference between active and total vitamin B12 in our blog.

Pernicious anaemia is an autoimmune disease that affects your body’s ability to absorb vitamin B12, causing vitamin B12 deficiency anaemia. Symptoms include feeling tired all the time, breathlessness, and mouth ulcers.

You’re more at risk of pernicious anaemia if you have a family history of the disease or another autoimmune condition, such as type 1 diabetes or a thyroid condition. If you’re concerned about pernicious anaemia, you can take a Pernicious Anaemia Blood Test.