Vitamin B12 is an essential vitamin for your body, Low levels cause fatigue, If you’re feeling tired and weak a vitamin B12 test might explain why.
Customize TestThe vitamin B12 blood test measures the level of serum vitamin B12 in your blood. It helps identify vitamin B12 deficiency, low B12 levels, or unusually high B12 levels that may affect energy, memory, and nerve function.
Vitamin B12 plays a key role in red blood cell formation, brain function, and metabolism. When levels fall below the normal vitamin B12 range, symptoms such as fatigue, numbness, or poor concentration may appear. This test evaluates vitamin B12 status and helps detect problems with B12 absorption or diet related deficiencies.
Vitamin B12 supports several critical functions in the body.
Key roles include:
• Production of healthy red blood cells
• Supporting nerve health and brain function
• Helping DNA synthesis and metabolism
• Maintaining memory and cognitive performance
• Preventing pernicious anemia and vitamin B deficiency symptoms
Low levels can lead to vitamin B12 deficiency symptoms, while extremely high levels may require further medical evaluation.
A low vitamin B12 level may cause a range of symptoms.
Common signs of vitamin B12 deficiency include:
• Fatigue and weakness
• Pins and needles in hands or feet
• Memory problems or brain fog
• Pale skin or anemia
• Mood changes or depression
• Difficulty concentrating
• Shortness of breath
People may also experience very low B12 symptoms if deficiency remains untreated for a long period.
Several factors can cause low B12 levels.
Common causes of vitamin B12 deficiency include:
• Poor intake of foods high in vitamin B12
• Vegan or vegetarian diet lacking B12 food sources
• Poor vitamin B12 absorption in the stomach or intestines
• Digestive conditions affecting nutrient absorption
• Long term medication use affecting vitamin absorption
• Age related reduction in stomach acid
Understanding the reasons for B12 deficiency helps guide treatment and diet changes.
Vitamin B12 mainly comes from animal based foods.
Common foods high in B12 include:
• Meat and poultry
• Fish and seafood
• Eggs
• Dairy products such as milk and cheese
• Fortified cereals and vitamin B12 enriched foods
If dietary intake is low, supplementation may help meet recommended daily vitamin B12 requirements.
Read more about b12 on healthline
The normal B12 levels in blood typically fall within a clinical reference range.
Typical vitamin B12 normal range:
• Normal: about 200 to 900 pg/mL
• Low: below 200 pg/mL may indicate deficiency
• High: above normal may require further investigation
Doctors may also assess active B12 holotranscobalamin, which shows the amount of B12 available for body cells.
In some cases, doctors may recommend additional tests to understand B12 metabolism.
These may include:
• Serum folate blood test
• Blood test folate
• Holotranscobalamin test or active B12 test
• Vitamin B12 and folate deficiency testing
These tests help identify functional B12 deficiency or combined nutrient deficiencies.
This blood test may benefit people who:
• Experience low B12 symptoms such as fatigue or numbness
• Follow a vegan or vegetarian diet
• Have digestive disorders affecting nutrient absorption
• Experience memory problems or neurological symptoms
• Have anemia or unexplained tiredness
• Want to check healthy B12 levels as part of preventive health testing
Key benefits include:
• Detect vitamin B12 deficiency early
• Identify causes of low vitamin B12
• Monitor vitamin B12 levels during treatment
• Assess nutrient status in health conscious individuals
• Support better energy, nerve health, and metabolism
Regular monitoring helps maintain optimal B12 levels for women and men.
Vitamin B12 supports nerve function, red blood cell production, and DNA synthesis. It also helps maintain energy levels and brain health.
Common symptoms include fatigue, numbness, memory problems, weakness, and pale skin.
Foods that contain B12 include meat, fish, eggs, milk, dairy products, and fortified cereals.
Adults generally require about 2.4 mcg per day to maintain healthy levels.
Doctors measure B12 using a serum vitamin B12 blood test, which checks the level of B12 circulating in the blood.
Yes. Low B12 levels may affect concentration, memory, and cognitive function because the vitamin supports healthy nerve cells.
Check out our vitamin d blood test
Vitamin B12 is part of the B complex of vitamins
The body is unable to make them itself and so instead must take them in through the diet
It contributes to your red blood cells metabolism and organ function