Vitamin B12, also called cobalamin, is a water-soluble vitamin that is essential for the proper functioning of the body. It plays a key role in:

• The formation of red blood cells : B12 helps produce red blood cells that carry oxygen throughout the body.
• Nervous system support : It participates in the formation of the protective sheath of nerves, called myelin, thus ensuring their proper functioning.
• DNA synthesis : It contributes to the production of DNA, the genetic material necessary for cell growth and repair.

Vitamin B12 levels are often tested to diagnose disorders related to blood health, neurological function, and digestion.

A vitamin B12 test can help detect deficiencies or high levels, indicating underlying health conditions such as anemia, absorption disorders, or certain liver and blood diseases.

A doctor may recommend testing vitamin B12 levels to monitor your health or if you have symptoms related to a deficiency or excess of B12. The following are the cases where this test is usually prescribed:

• Signs of vitamin B12 deficiency : Symptoms such as weakness, fatigue, memory loss, or tingling in the hands and feet.
• Chronic disease monitoring : For people with conditions like Crohn's disease, celiac disease, or pernicious anemia, which affect the absorption of B12.
• After gastric surgery : To check if your body is properly absorbing vitamin B12 after bariatric surgery or other stomach surgery.
• Vegan or vegetarian diets : Because B12 is mostly found in animal products, people on a plant-based diet may need regular testing to avoid a deficiency.
• Prolonged use of certain medications : Some medications may interfere with the absorption of B12, causing low levels over time.

Vitamin B12 is usually measured by a blood test. During this test, a health professional takes a blood sample from a vein in your arm. The sample is then analyzed in the lab to determine how much vitamin B12 is in your blood.

Other specialized tests may also include levels of B12:

• Complete blood count (CBC) : Measures various parts of the blood, including the size of red blood cells, to detect a B12 deficiency.
• Methylmalonic acid (MMA) test : High levels of MMA in blood or urine may indicate low vitamin B12.
• Intrinsic factor antibody test : Allows you to determine if your body is producing antibodies that attack the intrinsic factor, a protein necessary for the absorption of B12.

Preparations:

• Avoid eating for 6 to 8 hours before the test, if recommended by your doctor.
• Tell your healthcare professional what supplements or medications you are taking, as they may affect test results.
• Do not change your medication without your doctor's advice.

For adults, the normal range of vitamin B12 in the blood is generally between:

200 and 1100 pg/mL (picograms per milliliter)

Note : The units of measurement and the normal ranges may vary depending on the laboratory and the specific methods used.

Abnormal levels of vitamin B12 in the blood can indicate several health conditions, depending on whether they are too high or too low.

High levels
High levels of vitamin B12 are less common, but may signal underlying conditions, such as:

• Liver diseases : When the liver is damaged, it can release excessive amounts of vitamin B12 into the bloodstream.
• Polycythemia vera : A rare disorder where the body produces too many red blood cells, leading to high levels of B12.
• Leukemia : Some types of blood cancers can increase the amount of B12 in the blood.
• Kidney diseases : Impaired kidney function may prevent B12 from being properly filtered from the blood.

Recommendations:

• See your doctor to investigate the cause of the high levels.
• Monitor your blood tests regularly to keep track of your B12 levels.
• Make lifestyle adjustments based on your doctor's advice, possibly including dietary changes or treatment for the underlying condition.

Low levels
Low levels of vitamin B12 are more common and can lead to symptoms such as fatigue, nerve problems, and anemia. The causes include:

• Dietary deficiency : Vegan or vegetarian diets increase the risk of B12 deficiency, as the vitamin is mainly found in animal products.
• Pernicious anemia : A condition where the body cannot absorb B12 due to a lack of intrinsic factor.
• Gastric surgery : After some procedures, such as a gastric bypass, the body may have trouble absorbing B12 properly.
• Absorption disorders : Diseases like Crohn's disease or celiac disease hinder the absorption of nutrients, including B12.
• Aging : As we age, the body may become less efficient at absorbing B12.

Recommendations:

• Increase your intake of B12-rich foods: Eat more meat, fish, eggs, and dairy products. If you're vegan or vegetarian, opt for fortified foods like plant-based milks and cereals.
• Reduce your alcohol consumption: Alcohol can interfere with the absorption of B12.
• Stop smoking: Smoking can decrease the efficiency of B12 absorption.
• Follow up regularly: If you have a condition that affects absorption, see your doctor to monitor your B12 levels.
• Consider B12 supplements: If you have difficulty absorbing B12 through food, your doctor may recommend oral supplements or injections.

If you have abnormal levels of vitamin B12 or symptoms of deficiency or excess, it is important to see the right specialist:

• General practitioner : For an initial diagnosis and overall management of your condition.
• Gastroenterologist : In case of absorption problems related to the digestive system, such as Crohn's disease or after gastric surgery.
• Hematologist : For blood disorders such as anemia or polycythemia.
• Neurologist : If you experience nerve symptoms such as tingling or numbness, which are often related to a B12 deficiency.
• Nutritionist : To help you adjust your diet and ensure adequate vitamin B12 intake, especially if you follow a plant-based diet.