B12 blood test

Overview

A B12 blood test checks the amount of vitamin B12 in your blood. Vitamin B12 is important for making red blood cells and keeping your nerves healthy. The test helps find out if you have a shortage of this vitamin, which can cause tiredness, weakness, or nerve problems.

B12 deficiency is fairly common, especially in older adults, people with certain digestive conditions, and those on a strict vegan diet.

It can affect anyone, but is more common in older adults, vegetarians, vegans, people with stomach or intestinal conditions (like Crohn's or celiac disease), and those who have had stomach surgery.

Symptoms

Common symptoms

• Feeling very tired and weak
• Pale or yellowish skin
• Shortness of breath and dizziness
• Heart palpitations (feeling like your heart is racing or skipping beats)
• Numbness or tingling in your hands and feet
• Smooth, sore tongue
• Problems with memory or thinking clearly

Symptoms in children

• Slow growth and development
• Weakness and lack of energy
• Irritability or being very fussy
• Delays in reaching milestones like walking or talking

Symptoms in older adults

• Confusion or memory loss that may look like dementia
• Loss of balance and trouble walking
• Numbness or tingling in the hands and feet
• Fatigue and weakness

Causes

Main causes

• Not getting enough B12 from food (common in vegans and strict vegetarians)
• Problems absorbing B12 from food (due to conditions like pernicious anemia, Crohn's disease, or celiac disease)
• Medications that lower stomach acid or treat diabetes (like metformin)
• Stomach surgery that removes part of your stomach or intestine

Risk factors

• Age over 60
• Following a vegan or vegetarian diet without fortified foods or supplements
• Having a digestive disorder that affects nutrient absorption
• Having had weight loss surgery or stomach surgery
• Long-term use of acid-reducing medicines

When to see a doctor

See a doctor urgently if:

• If you have sudden confusion, difficulty walking, or severe shortness of breath

Book a routine appointment if:

• If you have ongoing tiredness, weakness, numbness, or tingling
• If you have a known condition that affects B12 absorption
• If you follow a strict vegan diet and notice symptoms of deficiency

Diagnosis

The B12 blood test is done with a simple blood draw, usually from a vein in your arm. Your doctor will order the test if you have symptoms of deficiency or are at risk.

Tests that may be done

• Vitamin B12 blood level test
• Folate (another B vitamin) test
• Complete blood count (CBC) to check for anemia
• Other tests like MMA and homocysteine levels for more detail

What to expect at your appointment

The blood test takes a few minutes. You do not need to do anything special to prepare, though your doctor might ask you to fast (not eat or drink) for a few hours before. Results usually come back in a few days. Your doctor will explain what your B12 level means and if any treatment is needed.

Treatment

If you have low B12, treatment aims to restore your vitamin levels to normal and relieve symptoms.

Self-care at home

• If you are vegetarian or vegan, eat B12-fortified foods like plant milks, breakfast cereals, and nutritional yeast.
• Take a B12 supplement if your doctor recommends one (always check the dose with your doctor or pharmacist).
• Eat more B12-rich foods like meat, fish, eggs, and dairy if you are not vegetarian.

Medical treatments

Your doctor may prescribe B12 injections or high-dose oral supplements, depending on the cause of your deficiency. For pernicious anemia or absorption problems, injections are common. For diet-related deficiency, oral supplements may work. Treatment is usually continued until your levels are normal, and sometimes lifelong if the underlying cause cannot be reversed.

When is surgery considered?

Surgery is not a treatment for B12 deficiency itself, but if the deficiency is caused by a condition that requires surgery, that would be managed separately.

Living with this condition

Once your B12 levels are restored, most people feel much better. You may need to continue supplements or injections as directed by your doctor. Keep your follow-up appointments to monitor your levels.

Lifestyle tips

• Stick to a balanced diet that includes B12 sources or fortified foods.
• Set reminders for taking supplements or scheduling injections.
• Stay active gently if you have nerve symptoms, and ask your doctor about physical therapy if needed.

Diet and exercise

Eating a diet rich in B12 helps prevent recurrence. For most people, exercise is safe and beneficial. If you have nerve pain or balance issues, talk to a physiotherapist about safe activities.

Mental health and emotional wellbeing

Low B12 can affect your mood and memory. After treatment, many people notice improved concentration and mood. If you feel anxious or depressed, talk to your doctor – they can help you get support.

Prevention

Yes, in many cases. Eating enough B12 in your diet or taking supplements if you are at risk can prevent deficiency. People over 60 or with absorption issues may need regular monitoring.

Vaccines

There are no vaccines for B12 deficiency.

Screening programmes

Routine screening is not recommended for everyone, but your doctor may test you if you have symptoms or risk factors. Pregnant women and people on certain medications may also be checked.

Complications

If left untreated

• Permanent nerve damage causing numbness, weakness, and balance problems
• Anemia (low red blood cells) leading to severe fatigue and heart problems
• Increased risk of depression and cognitive decline
• Problems with pregnancy including neural tube defects in the baby

Long-term outlook

When diagnosed early and treated, B12 deficiency is usually reversible. Most people feel much better within a few weeks of starting treatment. Even if some nerve symptoms take longer to heal, improvement is common. With the right treatment, you can live a normal, healthy life.

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