How to check vitamin B12 deficiency?

Author: Miss Maudie Aufderhar V  |  Last update: Tuesday, November 4, 2025

To screen for vitamin B12–deficiency anemia, your healthcare provider may order blood tests to see whether you have low hemoglobin or vitamin B12 levels. Tests to screen for vitamin B12-deficiency anemia. A complete blood count measures hemoglobin. Another blood test measures vitamin B12 levels in the blood.

How can I check if my B12 is low?

Different types of blood tests can be carried out to help identify people with a possible vitamin B12 or folate deficiency. These tests check: whether you have a lower level of haemoglobin (a substance that transports oxygen) than normal. whether your red blood cells are larger than normal.

How do doctors test for B12 deficiency?

An MMA test is most often used to diagnose a vitamin B12 deficiency. The test is usually also included as part of a series of tests called a newborn screening. A newborn screening checks for a variety of health conditions. An MMA test checks for methylmalonic acidemia, a rare genetic disorder.

What is the fastest way to fix B12 deficiency?

Vitamin B12 deficiency anaemia is usually treated with injections of vitamin B12, called hydroxocobalamin. At first, you'll have these injections every other day for 2 weeks or until your symptoms have started improving.

What is the #1 food highest in B12?

Top foods with B12
  • Clams, 3 ounces: 84 mcg.
  • 100% fortified breakfast cereal (check the label), 1 serving: 6.
  • Trout, 3 ounces: 5.4.
  • Salmon, 3 ounces: 4.9.
  • Canned tuna fish, 3 ounces: 2.5.
  • Fortified soy milk, chocolate (check the label): 1.7.
  • Beef, 3 ounces: 1.5.
  • Nonfat plain Greek yogurt, 6 ounces: 1.3.

Testing for Vitamin B12 Deficiency (Order THESE 4 Lab Tests)

What are the worst symptoms of B12 deficiency?

Symptoms of vitamin B12 deficiency
  • mouth ulcers.
  • pins and needles (paraesthesia)
  • changes in the way that you walk and move around.
  • disturbed vision.
  • irritability.
  • depression.
  • changes in the way you think, feel and behave.
  • a decline in your mental abilities, such as memory, understanding and judgement (dementia)

How long after starting vitamin B12 will I feel better?

It may take a few weeks before your vitamin B12 levels and symptoms (such as extreme tiredness or lack of energy) start to improve. If you have hydroxocobalamin injections to boost your vitamin B12 levels at the start of treatment, the cyanocobalamin tablets may start to work within a few days.

What are the facial signs of B12 deficiency?

The deficiency of vitamin B12 can cause specific skin manifestations, such as hyperpigmentation, vitiligo, angular stomatitis, and hair and nail changes [1].

What organ is affected by B12 deficiency?

If vitamin B12 deficiency is left untreated, it can cause lasting side effects that affect the nervous system and brain. More severe side effects of vitamin B12 deficiency include: Peripheral neuropathy. Degeneration of the spinal cord.

What does B12 fatigue feel like?

Weakness. Your muscles may lack strength. You also might feel tired or lightheaded. Your doctor can check how much B12 is in your body, but not all of it may be useable.

What blocks B12 absorption?

Conditions affecting the stomach

Some stomach conditions or stomach operations can prevent the absorption of enough vitamin B12. For example, a gastrectomy, a surgical procedure where part of your stomach is removed, increases your risk of developing a vitamin B12 deficiency.

What does low B12 feel like?

Symptoms include weak muscles, numbness, trouble walking, nausea, weight loss, irritability, fatigue, and increased heart rate. Treatment may include vitamin B12 supplements. It is also important to eat a well-balanced diet.

Can you take vitamin B12 without seeing a doctor?

If you do not have any of the conditions below then it is likely that your low vitamin B12 is due to your diet, in which case it is not a medical issue and can be corrected with oral supplements you can buy over the counter or online.

What foods should be avoided if you have B12 deficiency?

Avoid foods rich in fiber

Foods high in fiber, particularly soluble fiber, can interfere with the absorption of B12. Fiber binds with B12 and prevents its absorption in the small intestine.

What is the fastest way to recover from B12 deficiency?

Ways to Manage Your B12 Deficiency
  1. Shots. They can put B12 directly into your muscle with a needle. This bypasses your stomach. ...
  2. Nasal spray. If you don't like needles, ask your doctor about a prescription nasal spray. ...
  3. Dietary supplements. You can swallow a pill or take a tablet that melts under your tongue.

Can you take too much B12?

While the recommended daily amount of vitamin B-12 for adults is 2.4 micrograms, higher doses have been found to be safe. Your body absorbs only as much as it needs, and any excess passes through your urine. High doses of vitamin B-12, such as those used to treat a deficiency, might cause: Headache.

Why are doctors stopping B12 injections?

Coronavirus has made it necessary to move patients on B12 injections to oral treatment. Reason: RISK REDUCTION in terms of limiting your movement outside your home and contact with our staff and nurses. Nationally all NHS organisations will be stopping injections during this difficult time.

What does B12 acne look like?

High-dose vitamins B6 and B12 have also been linked to rosacea fulminans, a condition that looks like acne. Rosacea is marked by large red bumps and pustules that typically appear on the nose, chin, and/or cheeks.

What medications should not be taken with B12?

Summary: As summarized in the table provided, vitamin B12 (cobalamin) absorption and utilization by the body can be compromised with the chronic use of certain medications which include: colchicine, chloramphenicol, ethanol, histamine 2 receptor antagonists (H2RA), metformin, and proton pump inhibitors (PPI).

What deficiency causes tingling in hands and feet?

Untreated, vitamin B-12 deficiency can lead to neurological problems, such as persistent tingling in the hands and feet or problems with balance. It can lead to mental confusion and forgetfulness because vitamin B-12 is necessary for healthy brain function.

Is it okay to take 1000 mcg of B12 a day?

Even the lowest doses in B12 supplements are many times the recommended dietary allowance. Doses up to 1,000 mcg, though unnecessary, aren't harmful. Fortified foods. Many breakfast cereals, soy products, and yeasts are fortified with B12.

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