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What's the Right Vitamin B12 Dosage for Older Adults?

What's the Right Vitamin B12 Dosage for Older Adults?

What's the Right Vitamin B12 Dosage for Older Adults?

Vitamin B12 deficiency is common among older people, affecting an estimated 10%-15% of people over60. This is often due to malabsorption issues such as gastritis and pernicious anemia.

Although general guidelines recommend a dosage of just 2.4mg per day for people over 14, this amount may not account for absorption issues affecting older people.

This article will discuss the risks of B12deficiency in older age groups and the serious consequences this can have for both short- and long-term health. We will explain how to identify a B12deficiency and the best options for treatment.

The Risks of Vitamin B12 Deficiency as You Get Older

Between 10-30percent of people over 50 produce too little stomach acid, often due to atrophic gastritis and reduced secretion of pepsin by the gastric mucosa. This reduces the ability to absorb B12 from food. Low acid may also cause bacterial overgrowth of the stomach and small intestine. These bacteria may then bind to vitamin B12 for their own use.

Pernicious anemia is also more prevalent in older age groups and reduces intrinsic factor required for B12 absorption. Disorders and surgery to the gastrointestinal system may also reduce absorption.

A B12 deficiency can have severe health implications for older people. If untreated, the nervous system can suffer progressive damage, especially the nerves outside the brain and spinal cord.

Hematological changes may include:

  • Pancytopenia(reduced red and white blood cells and platelets)

  • Macrocytosis(enlarged red blood cells)

  • Hypersegmentationof neutrophils (a sign of megaloblastic anaemia)

  • Hypercellularbone marrow (abnormally high numbers of cells)

Older adults with B12 deficiency are also at higher risk of cardiovascular diseases such as atherosclerosis and thrombotic events. This is due to elevated homocysteine resulting from inadequate B12 in the homocysteine-methionine conversion process.

Neuropsychiatric manifestations resulting fromB12 deficiency may include paraesthesia, weakness, gait abnormalities, and cognitive or behavioral changes. It has been shown that low serum vitamin B12is associated with a higher risk of cognitive impairment. Low B12is also significantly higher in people with Alzheimer’s disease.

Older adults may also suffer irreversible loss of neurological function. Severe symptoms due to nerve damage may last for months or years and may be permanent. Loss of mental function caused by vitaminB12 deficiency is unlikely to return after treatment.

How Do You Identify a Vitamin B12 Deficiency?

Many of the initial symptoms of vitamin B12deficiency are associated with anemia. These include fatigue, lightheadedness, muscle weakness, pallor, shortness of breath, and difficulty hearing and walking.

Damage to the spinal cord can lead to loss of sensation and/or ataxia (loss of muscle coordination). Other signs of B12 deficiency may include weight loss, poor reflexes, mild depression and confusion, hallucinations, and changes in personality and mood.

At present, there is no consensus or guideline for diagnosing B12 deficiency. Diagnosis is often based on clinical symptoms, low B12 test results, and elevated homocysteine or methylmalonic acid. A patient's response to treatment can also contribute to a diagnosis.

Treating a Vitamin B12 Deficiency

Treatment of vitamin B12 deficiency or pernicious anemia consists of high doses of vitamin B12 supplements. Regular blood tests are then required to ensure B12 level returns to normal.

People with severely low B12 levels or neurological symptoms will usually be treated with B12 intramuscular injections. These may be self-administered and are given daily or weekly for several weeks until the vitamin B12 level returns to normal. Injections are then given once a month or until the cause of the deficiency can be corrected.



B12 is created by bacteria that colonize the gut, which means its natural form is only present in animal products such as milk, cheese, eggs, and organ meats.

  • Organ meats: liver, kidney, heart

  • Shellfish: clams

  • Meat: beef, pork, poultry

  • Fish: trout, salmon, tuna

  • Dairy products: unsweetened yogurt, milk,cheese

  • Eggs

  • Fortified cereals, bread

Food sources are unlikely to restore a deficiency due to the inability to absorb food-bound B12. The bioavailability of vitaminB12 from food also varies by the type of food source and by an individual’s capacity of intrinsic factor.


Because a large proportion (up to 30%) of adults aged 50+ have a higher risk of malabsorption due to gastrointestinal disorders and/or poor stomach acid, it is recommended that they meet the RDA (Recommended Dietary Allowance) for vitamin B12 with supplements. B12 is reported to be about 50% more bioavailable in dietary supplements than in food sources.

Successful treatment and management of a deficiency may require lifelong oral supplementation or periodic intramuscular injections.

Cyanocobalamin is most often used in B12supplements, and high doses (1mg) are required because the lack of intrinsic factor requires absorption by passive diffusion from the gut.

However, the three naturally-occurring forms ofB12 (Methylcobalamin, Hydroxocobalamin, and Adenosylcobalamin) are shown to improve vitamin B12 status more effectively in lower doses than cyanocobalamin.

A meta-analysis found that supplementing with oral B12 in 2000 mcg doses daily and 1000 mcg doses initially daily and then weekly/monthly may be as effective as intramuscular administration in providing short-term hematological and neurological benefits in patients with B12 deficiency.

Key Takeaways

Those aged 50+ should be aware of their higher risk of developing B12 deficiency and the implications for their long-term health. The recommended intake of 2.4mg may not be sufficient to maintain healthy levels of this crucial nutrient.

Vitamin B12 deficiency can have serious and potentially irreversible consequences, particularly in terms of neurological function. Although it is advisable to focus on eating plenty of B12-rich foods, malabsorption issues mean that food alone may not be enough to restore and maintain adequate levels.

Severe deficiency will require intramuscular injections to correct anemia and/or prevent neurological complications. However, oral supplementation with active forms of B12 may also be highly effective in restoring B12 levels.

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    Written By,
    - Katie Stone



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