The Recommended Vitamin B12 Dosage For Seniors

Health problems caused by a deficiency in vitamin B12 are not uncommon among us in the over-50 crowd, so it’s important we get enough B12 daily.

This article provides the recommended B12 dosages according to the various nutritional needs of older adults, and discusses the factors that influence how much vitamin B12 we each need.


How much B12 should seniors take?

The daily RDA (recommended dietary allowance) for vitamin B12 for healthy adults is 2.4 mcg (micrograms), per guidelines set by the National Academy of Medicine. 

However, medical researchers have indicated that many older adults may need a higher dose than this, because they’ve found vitamin B12 deficiency in a significant percentage of seniors.


What’s next

Ahead we’ll look at the more common reasons for vitamin B12 deficiency in older adults and the ways used to fix it, depending on the cause.

I’ll also provide a list of the foods highest in B12 and talk a little about B12 supplementing too.

Next though, I want to briefly run through why it’s important not to become vitamin B12 deficient.



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Science resources included

As is my custom here on heydayDo, I will provide links to all of the relevant sports science & medical resources, clinical studies, and nutritional data used in this article.



Risks & symptoms of B12 deficiency

This section’s all about why you never want to become B12 deficient; it’s nothing but bad news.

According to the National Institute of Health (1), a deficiency in B12 can cause:

  • anemia
  • fatigue
  • weakness
  • constipation
  • loss of appetite
  • weight loss
  • soreness of the mouth or tongue


Chalkboard with chemistry diagram of molecules in Vitamin B12


The NIH also says that B12 deficiency may have the following neurological & psychological symptoms as well:

  • difficulty maintaining balance
  • confusion
  • dementia
  • numbness and tingling in the hands and feet


What happens if B12 deficiency is untreated?

Per Harvard Medical, “if left untreated, the deficiency can cause severe neurologic problems and blood diseases” (2).

In their report on vitamin B12 deficiency, Harvard Medical states that severe instances have led to:

  • deep depression
  • paranoia and delusions
  • memory loss
  • incontinence
  • loss of taste and smell
  • and more.


Permanent damage is possible

The NIH warns that it’s critical to detect & treat B12 deficiency in its early stages, otherwise you run the risk of incurring “irreversible damage”. (3)

This dire message is echoed by the director of Mayo Clinic’s Healthy Living Program, Dr. Donald Hensrud, who states that those physical & mental health issues listed above

“can progress if left untreated, and can lead to irreversible damage.” (4)


Recovery quality related to symptom length

On the good news side of the ledger, most patients respond well to B12 deficiency treatment.

It’s just that the degree of positive response is related to how long before treatment the symptoms had been going on, and how severe they had been.

Those were the findings of a 17-year vitamin B12 deficiency study conducted at two New York City hospitals, where physicians were able to reduce the symptoms’ severity score by “50% or greater after treatment in 91%” of the patients (5).


Those results obviously underscore the importance of early diagnosis & treatment for B12 deficiency.


Those symptoms are similar to other senior issues

One thing you may have thought of as you read through those lists is that many of those same symptoms occur due to a number of other health issues that older adults may experience.

Health issues that are unrelated to being deficient in vitamin B12.

In their health letter recommending B12 supplementation for older adults, the Mayo Clinic puts it like this:

“Since the symptoms are similar to many other conditions associated with aging, it’s sometimes overlooked.” (6)


That’s why it’s important to see your doctor & discuss a simple blood test for B12 deficiency if you’re experiencing any of those symptoms.



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Most common cause of B12 deficiency

In that 17-year research study on B12 deficiency I mentioned earlier, the authors stated that

“Pernicious anemia was the most common underlying cause of the deficiency”. (7)


The NIH describes pernicious anemia as follows:

Pernicious anemia (per-NISH-us uh-NEE-me-uh) is a condition in which the body can’t make enough healthy red blood cells because it doesn’t have enough vitamin B12. (8)


Medical research indicates that pernicious anemia is responsible for up to 50% of the B12 deficiencies reported (9).

Other causes of vitamin B12 deficiency include:

  • Crohn’s & celiac diseases
  • weight loss bypass surgery (gastrectomies)
  • use of antacids
  • a B12 deficient diet
  • digestive tract infection


B12 deficiency chances increase with age

Mayo Clinic notes that vitamin B12 deficiency “develops slowly and is more common with increasing age.” (10)


Aging & decreased nutrient absorption

Another factor in B12 deficiency is somewhat age-related.

The National Institute of Health reports that between 10%-30% of the older adult population is affected by atrophic gastritis. (1)


This is a condition where your stomach doesn’t make enough acid to break down your food properly. As a result you don’t get all the nutrients your food had in it.

And this includes the B12 found in meats, fish, & dairy foods.

The result is a slow-developing B12 deficiency, despite the fact that the diet included enough B12 in it.



B12 deficiency treatment options

Vial & chart for senior getting blood test for vitamin B12 deficiency


As mentioned earlier, asking your doctor for a B12 blood test is a good idea if you’re an older adult and noticing anything like those B12 deficiency symptoms I listed earlier in the article.

Catching it early (if it’s even there in the first place) has been shown to greatly improve any symptoms (11).

Per the Mayo Clinic, if the B12 deficiency is mild, adding B12-rich food to your diet or taking a supplement might do the trick (12).

B12 supplements come in pill form, dissolvable sublingual tablets or drops, and even in nasal sprays.

Shop for vitamin B12 online


If it’s more severe than that, B12 injections are the usual course of action.

How bad the B12 deficiency is will have a lot to do with how often the B12 injections are needed.

Most people respond well to injections, and so they end up needing them less often as time goes by.


However, for some people who either can’t absorb it, don’t eat enough of it, or waited too long to treat it, B12 injections will be required for the rest of their life (13).


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Vitamin B12 dosage FAQ

Here are a few more of the commonly asked questions regarding vitamin B12 dosage & deficiency.


Why do food labels say B12’s RDI is 6mcg, not 2.4?

Food labels are managed by the Food & Drug Administration (our FDA).

Their term RDI, which stands for reference daily intake, is not the same thing as the National Academy of Medicine’s recommended dietary allowance (RDA) that we hear about when nutritionists, dietitians, & doctors discuss things we eat & drink.

This has created a little confusion amongst people who’re trying to pay attention to their nutrition, as you might imagine.


As a result, these two organizations got together and decided that the FDA will change all of their food label RDI amounts to the NAM’s recommended dietary allowance amounts (17).

This is a massive overhaul of course, and so they’re expected to have it completed sometime in 2020.

As far as B12 is concerned, once the FDA changes their labels you’ll see 2.4 micrograms listed as the RDA.

What foods are the highest in vitamin b12?

Remembering that the Recommended Dietary Allowance (RDA) for vitamin B12 is 2.4 mcg (micrograms) for older adults, here is a list of foods high in B12:


Vitamin B12 Food Serving size B12 (mcg)
Clams 3 ounces 84
Liver 3 ounces 70.7
Fortified cereal 1 cup 6
Trout 3 ounces 5.4
Salmon 3 ounces 4.9
Tuna, canned 3 ounces 2.5
Beef 3 ounces 1.5
Nonfat plain Greek yogurt 6 ounces 1.3
Low-fat milk 1 cup 1.2
Ham 3 ounces 0.6
Egg 1 large 0.6
Chicken breast 3 ounces 0.3

An even more extensive listing of B12 quantities in foods can be found in this PDF document issued by the Dietitians of Canada.


Which fruits & vegetables have vitamin B12?

Fruits & vegetables have negligible amounts of vitamin B12 in them.

The only (non-dairy/non-egg) vegetarian sources for B12 are:

  • fortified cereals
  • fortified milk substitutes like fortified soy or almond milk
  • nutritional yeast
  • nori
  • shiitake mushrooms (16).

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Wrapping Up

I hope that my article on vitamin B12 dosages for seniors & B12 deficiencies is useful to you, and that the list of foods high in B12 is helpful too.

I wish you well on your fitness journey; let’s go.

– greg

July 2020


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About Me

heydayDo author Greg Simon
Hi I’m Greg Simon. Fitness training & nutrition researching since 1982. Surfer. Organic food & wine grower. Guitarist & music producer. Congenital heart disease survivor (so far).

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About heydayDo

heydayDo is my “fitness after 50” website that’s about embracing the physically active lifestyle as we get older.
It’s an information-sharing, personal opinion blog of mine.
(So if you’re looking for medical advice, hit up your doctor or health professional for that. I’m just shootin’ the breeze here…) 
heydayDo began as a daily journal I kept as I recovered from the latest of many heart operations I’ve had to deal with since birth. 
I have a deep interest in learning about nutrition & fitness, and applying it to improve my quality of life.
I believe this knowledge can help me be the healthiest & strongest version of me as I can, even in the face of inborn heart disease.
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The 60-year-old version of me, January 2020

So when I get curious about something, I’ll dig into whatever sports science & medical facts there are on the topic to learn what’s real & what’s hype.
Here on heydayDo I share what I’ve learned from my fitness, health, & nutrition research with whoever drops by.