Feeling constantly tired, experiencing memory problems, or wondering if your fatigue and neurological symptoms could be related to vitamin B12 deficiency?
The Vitamin B12 Blood Test measures levels of B12, a vitamin essential for making red blood cells, protecting nerves, and supporting energy production. Low B12 can cause fatigue, anaemia, memory issues, and nerve problems, while healthy levels are vital for brain function and overall wellbeing.
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The Vitamin B12 Blood Test measures levels of B12, a vitamin essential for making red blood cells, protecting nerves, and supporting energy production. Low B12 can cause fatigue, anaemia, memory issues, and nerve problems, while healthy levels are vital for brain function and overall wellbeing.
Think of Vitamin B12 as your body's master electrician and energy crew chief all rolled into one. This essential vitamin keeps your nerve pathways running smoothly like well-maintained electrical wiring, while also supervising the production of healthy red blood cells that carry oxygen throughout your body. The B12 test measures how much of this crucial vitamin is circulating in your blood, giving you a clear picture of whether your body has enough fuel to keep your nervous system sharp and your energy levels steady.
When B12 levels drop too low, it's like having faulty wiring in your house – you might experience tingling or numbness in your hands and feet, brain fog, unusual fatigue, or even mood changes. This test is especially valuable if you follow a vegetarian or vegan diet (since B12 is mainly found in animal products), have digestive issues that might prevent proper vitamin absorption, or have been feeling unusually tired or mentally foggy. By catching B12 deficiency early, you can address it with targeted supplements or dietary changes before it leads to more serious nerve damage or anemia, helping you maintain the sharp thinking and steady energy your body depends on.
You may benefit from the Vitamin B12 Blood Test
Critical for vegetarians, vegans, and people over 50 who have increased risk of deficiency. Essential for those experiencing unexplained fatigue, memory problems, mood changes, or neurological symptoms. Important for individuals with digestive conditions, those taking certain medications (particularly proton pump inhibitors or metformin), or anyone with symptoms suggesting B12 deficiency.
Feeling tired all the time
Extreme fatigue that doesn't improve with rest
Difficulty concentrating on tasks
Mind feeling foggy or cloudy
Problems with short-term memory
Tingling in hands or fingers
Numbness in feet or toes
Feeling sad or down most of the time
Memory problems or confusion
Weakness or unsteadiness
Mental fatigue or brain tiredness
Trouble focusing during conversations
Difficulty remembering names
Difficulty following conversations
Pins and needles sensation
Difficulty with balance while walking
Falls or near-falls due to balance issues
Feeling worthless or guilty
Problems with organization
Back pain that radiates down legs
Tingling in hands and feet
Raw food diet concerns
Memory problems in elderly
Hearing loss with aging
How to prepare
No fasting required. Can be taken at any time of day. If taking B12 supplements, maintain your usual routine unless specifically advised otherwise by your healthcare provider. Avoid biotin supplements for 3 days before testing as they can interfere with results.
Understanding results
Normal range: 180-900 pmol/L (240-900 ng/L). Deficient: <180 pmol/L; Borderline: 180-300 pmol/L; Sufficient: >300 pmol/L. Some experts recommend levels above 400 pmol/L for optimal function. Low levels may indicate dietary deficiency, absorption problems, or pernicious anaemia. Very high levels are rarely harmful but may indicate liver disease or certain blood disorders.
After the test
If levels are low or borderline, discuss B12 supplementation with your healthcare provider. Treatment typically involves oral supplements or injections depending on the cause and severity. Additional testing may include methylmalonic acid (MMA) and homocysteine to confirm functional B12 status. Investigate underlying causes such as dietary intake, absorption issues, or autoimmune conditions. Retest in 3-6 months to monitor treatment effectiveness.
Frequently Asked Questions
B12 is unique because it's the only vitamin that contains a metal (cobalt), requires complex absorption mechanisms, can be stored in the liver for years, and is found almost exclusively in animal products.
It's extremely difficult for vegans to get adequate B12 from food alone since it's primarily found in animal products. Fortified foods and supplements are essential for vegans to prevent deficiency.
Standard B12 measures total vitamin including inactive forms, while Active B12 (holotranscobalamin) measures only the form that can actually be used by cells, providing a more accurate picture of functional status.
B12 injections typically maintain elevated levels for 1-3 months, but frequency depends on individual absorption, underlying conditions, and severity of deficiency. Your doctor will determine the appropriate schedule.
B12 is water-soluble and excess amounts are usually excreted safely. However, very high levels may indicate liver disease, kidney problems, or certain blood disorders requiring investigation.
B12 supplements only improve energy if you're actually deficient. Taking B12 when levels are already adequate won't provide additional energy benefits.
Reviewed by Dr. Vu Tran Bloody Good’s Chief Medical Officer
Bloody Good is a single portal for ordering, tracking, and reviewing on-demand health testing.
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