Vitamin B12 Test — Why B12 & Folate Levels Matter for Your Health

Feeling tired, foggy or run-down is common, especially for busy Londoners. Two key nutrients that often explain these symptoms are Vitamin B12 and folate (Vitamin B9). In this guide, we explain what they are, why they matter, what a blood test can show, and what low or high levels generally mean.
If you’re searching for a Vitamin B12 test London, this article will help you understand exactly what the test looks for and how it can help.

What are Vitamin B12 and Folate?

Vitamin B12 and folate are essential B-vitamins needed for:

• Making red blood cells
• Supporting the nervous system
• Helping cells grow and repair
• Supporting healthy pregnancy (folate)

Both work closely together. When either is low, your body struggles to produce healthy blood cells and maintain normal nerve function.

Different Types of B12 and Folate

Vitamin B12 forms

• Cyanocobalamin – common supplement form
• Methylcobalamin – active form used directly by the body
• Hydroxocobalamin – given in NHS injections
• Active B12 (Holotranscobalamin) – the part your cells can actually use

Folate vs Folic Acid

• Folate – natural form found in foods (greens, beans, liver)
• Folic acid – synthetic, stable form found in supplements and fortified foods
• Methylfolate – bioactive form used when people have difficulty converting folic acid

Why B12 & Folate Are Important for the Body

These nutrients play major roles in:

• Energy levels
• Memory and brain function
• Nerve health
• Red blood cell production
• Pregnancy development (folate prevents neural tube defects)

Deficiency can cause nerve damage, anaemia, and long-term complications if untreated.

Who Is at Risk of Low Levels?

You may be more likely to have low B12 or folate if you:

• Follow a vegan or vegetarian diet
• Are over 50
• Have stomach or gut conditions such as Crohn’s or coeliac disease
• Take metformin or long-term acid-reducing medication
• Are pregnant
• Have increased alcohol intake
• Have malabsorption issues (e.g., pernicious anaemia)

What a Blood Test Measures

A Vitamin B12 blood test typically checks:

• Serum Vitamin B12
• Active B12 (Holotranscobalamin)
• Folate
• Add-on tests if needed: Homocysteine and Methylmalonic Acid (MMA)

These additional markers help confirm early or borderline deficiencies even when the standard B12 test looks normal.

What Low Levels Generally Mean

Low Vitamin B12

Often caused by:

• Diet lacking animal products
• Poor absorption
• Pernicious anaemia
• Gut disorders
• Certain medications

Symptoms may include:

• Fatigue
• Pins and needles
• Memory issues
• Mood changes
• Pale skin
• Shortness of breath

Low Folate

Often caused by:

• Low dietary intake
• Pregnancy
• Alcohol use
• Certain medications
• Malabsorption

Symptoms overlap with B12 deficiency, but treatment differs.

What High Levels Generally Mean

High B12

Usually due to supplements or injections.
Occasionally linked to liver or blood disorders — should be reviewed if unexpectedly high.

High Folate

Typically from supplements or fortified foods.
Important: very high folic acid may hide signs of B12 deficiency, so both are often tested together.

Natural vs Artificial Supplements Explained

Natural Folate

• Found in leafy greens
• Easily used by the body
• Absorption varies with cooking and digestion

Folic Acid (synthetic form)

• More stable
• Widely used in supplements
• Must be converted into active folate in the body
• Some individuals (MTHFR variants) benefit from methylfolate instead

Getting a Vitamin B12 Test in London at The Scan Clinic

At The Scan Clinic, your B12 and folate levels can be checked quickly and accurately, please click here to learn more. Tests are performed by experienced clinicians, with fast turnaround and clear result explanations.

When You Should Consider Testing

You should consider a Vitamin B12 test if you have:

• Ongoing tiredness
• Low mood
• Difficulty concentrating
• Tingling in hands/feet
• Unexplained anaemia
• Vegan/vegetarian diet
• Gut health issues
• Pregnancy or planning pregnancy

If you’re concerned about your symptoms or want peace of mind, book your Vitamin B12 test in London at The Scan Clinic today.