Understanding the marker
Vitamin B12 supports nerve function and the formation of red blood cells. The blood test is one part of assessing the body's supply of this vitamin.
B12 is assessed with symptoms, dietary and absorption history and other blood tests. Nerve symptoms related to deficiency can occur even when the blood count is within its interval. Uncertain results may need a test such as methylmalonic acid, which adds information about B12 availability.
What does high Vitamin B12 mean?
High B12 often follows supplements or injections. A persistent unexplained elevation should be assessed in its clinical context.
What does low Vitamin B12 mean?
Low B12 can support a finding of deficiency. Symptoms such as altered sensation still need assessment even with a blood count within range. Borderline results may require additional testing, depending on symptoms and the clinical history.
Panels that measure Vitamin B12
Nutrient Essentials
Energy & Fatigue
Midlife Health
Plant-Based Living
Energy & Fatigue Plus
Northstar
Runner's Health
Vitals Pro
Menstrual Health Advanced
Fitness Premium
Vitals Max
Founders Panel Plus
Reading
- Tired all the time? The blood values that can explain why
- Trying for a baby: the blood tests worth taking first
- Vitamin D deficiency: symptoms, levels and what the Swedish winter does
- Normal TSH but still tired: what could be behind it?
- What is included in a blood test health check?
- Blood tests without a referral: how it works in Sweden
More markers in the same area
- Vitamin D (25-OH)the blood measure used to assess vitamin D supply
- Folate (B9)helps your body make new cells
- Vitamin A (Retinol)for vision, immunity, and skin
- Vitamin E (alpha-Tocopherol)a vitamin that helps protect cell membranes
- Holotranscobalaminthe portion of B12 available for cells to take up
- MagnesiumFor muscle and nerve function
This is general information about the marker, not an assessment of your values and not medical advice. Last updated: October 2026.