How to Detect & Treat Vitamin B12 Deficiency in Older Adults

Everyone knows that vitamins and nutrition are important for health, and many older adults take a multivitamin.

But did you know that even among older persons who do this, many still end up developing a serious deficiency in one particular vitamin?

It’s Vitamin B12.

If there’s one vitamin that I’d like all older adults and family caregivers to know more about, it would be vitamin B12.

(Second on my list would be vitamin D, but it’s much harder to develop low vitamin D levels if you take a daily supplement, as I explain in this post. Whereas vitamin B12 deficiency does develop in many older adults who are getting their recommended daily allowance.)

A deficiency in any vitamin can be catastrophic for health. But vitamin B12 deficiency stands out because a) it’s very common — experts have estimated that up to 20% of older adults may be low in this vitamin — and b) it’s often missed by doctors.

Geriatricians also like to pay attention to vitamin B12 because a deficiency can cause — or usually worsen — cognitive impairment or walking problems.

But if you know the symptoms and risk factors, you can help ensure that you get a vitamin B12 deficiency detected. Treatment is safe and effective, as long as you catch the problem before permanent damage occurs. Here’s what to know.

Symptoms of Vitamin B12 Deficiency & How it Harms Health

In the body, vitamin B12 – also known as cobalamin — is especially vital to making red blood cells, and maintaining proper function of nerve cells. When vitamin B12 levels are low, a person can develop health problems related to red blood cells and nerve cells malfunctioning. 

The most common problems related to low vitamin B12 levels include:

• Anemia. This means the red blood cell count is low. Red blood cells carry oxygen in the blood, so anemia can cause symptoms such as fatigue or shortness of breath. The breakdown of faulty red blood cells can also cause jaundice. (Learn more about anemia here: Anemia in the Older Adult: 10 Common Causes & What to Ask.)
• Neuropathy. This means that nerves in the body are not working well. This can cause a variety of symptoms, including tingling, numbness, burning, poor balance, and walking difficulties.
• Cognitive impairment. This means that nerve cells in the brain are not working well. This can cause symptoms such as memory problems, irritability, and even dementia.

You may have heard that vitamin B12 deficiency can cause pernicious anemia. But in fact, the term “pernicious anemia” means a specific vitamin B12 deficiency caused by the loss of the body’s ability to make “intrinsic factor.” Intrinsic factor is in the lining of the stomach, so a weakened stomach lining (which is called “atrophic gastritis” can cause pernicious anemia. The body needs intrinsic factor to absorb vitamin B12; without it, vitamin B12 levels eventually drop. This often causes anemia, but sometimes symptoms of nerve and brain problems occur first.

Why Low Vitamin B12 Levels Are Common in Older Adults

To understand how low vitamin B12 levels happen in aging adults, it’s good to start by learning how the body usually obtains and processes this vitamin.

In nature, vitamin B12 is available to humans only in meat and dairy products. However, in modern times, you can easily get it via a supplement or multivitamin. The recommended daily allowance for vitamin B12 for adults is 2.4 micrograms. Experts have estimated that a Western diet contains 5-7 micrograms of vitamin B12, and a multivitamin often contains 12-25 micrograms. 

Once you ingest vitamin B12, it is processed by acids and enzymes in the stomach and small intestine. The processed vitamin is then absorbed by the small intestine and stored in the body, especially in the liver. 

This stash can actually meet the body’s needs for a few years; although vitamin B12 is essential, only a tiny bit is needed every day. So if a healthy person stops taking in vitamin B12, it often takes a few years before the body runs out of it and develops symptoms of vitamin B12 deficiency.

So why does vitamin B12 deficiency particularly affect older adults?

As people get older, their ability to absorb vitamin B12 decreases. This is because aging adults often develop problems with the acids and stomach enzymes needed to process the vitamin. I go into this topic further in my Youtube video about B12:

Common risk factors for low vitamin B12 levels in older adults include:

• Low levels of stomach acid. This can be due to weakening of the stomach lining (also known as “atrophic gastritis”), or to medications that reduce stomach acid. 
• Medications such as metformin (used for diabetes), which interferes with vitamin B12 absorption.
• Alcoholism, which irritates the stomach and sometimes is linked to a poor diet.
• Surgeries to remove parts (or all) of the stomach or small intestine.
• Any problem that causes poor absorption in the stomach or small intestine, such as Crohn’s disease.

Why Vitamin B12 Deficiency Is Often Missed in Aging Adults

Vitamin B12 deficiency is often missed because the symptoms – fatigue, anemia, neuropathy, memory problems, or walking difficulties – are quite common in older adults, and can easily be caused by something else.

Also, vitamin B12 deficiency tends to come on very slowly, so people often go through a long period of being mildly deficient. During this time, an older person might have barely noticeable symptoms, or the symptoms might be attributed to another chronic health condition. 

Still, a mild deficiency will almost always get worse over time. And even when an older adult has many other causes for fatigue or problems with mobility, it’s good to fix whatever aggravating factors – such as a vitamin deficiency — can be fixed.

Unlike many problems that affect aging adults, vitamin B12 deficiency is quite treatable. Detection is the key;  then make sure the treatment plan has raised the vitamin B12 levels and kept them steady.

Who Should Be Checked for Vitamin B12 Deficiency

An older person should probably be checked for Vitamin B12 deficiency if he or she is experiencing any of the health problems that can be caused by low levels of this vitamin. 

I especially recommend checking vitamin B12 levels if you’re concerned about memory, brain function, neuropathy, walking, or anemia. 

To make sure you aren’t missing a mild vitamin B12 deficiency, you can also proactively check for low vitamin B12 levels if you or your older relative is suffering from any of the common risk factors associated with this condition.

For instance, you can request a vitamin B12 check if you’re vegetarian, or if you’ve suffered from problems related to the stomach, pancreas, or intestine. It’s also reasonable to check the level if you’ve been on medication to reduce stomach acid for a long time.

How Vitamin B12 Deficiency is Diagnosed

The first step in checking for deficiency is a blood test to check the serum level of vitamin B12.

Because folate deficiency can cause a similar type of anemia (megaloblastic anemia, which means a low red blood cell count with overly-large cells), doctors often test the blood for both folate and vitamin B12. However, folate deficiency is much less common. 

You should know that it’s quite possible to have clinically low vitamin B12 levels without having anemia. If a clinician pooh-poohs a request for a vitamin B12 check because an older person had a recent normal blood count, you can share this research article with the clinician.

Although MedlinePlus says that “Normal values are 160 to 950 picograms per milliliter (pg/mL)”, the clinical reference UptoDate says that a normal serum vitamin B12 level is above 300 pg/mL.

Normal vitamin B12 levels do not change with age, so there’s no need to look for a different cutoff as people get older.

If the vitamin B12 level is borderline, a confirmatory blood test can be ordered. It involves testing for methylmalonic acid, which is higher than normal when people have vitamin B12 deficiency.

In my own practice, especially if an older person has risk factors for vitamin B12 deficiency, I consider a vitamin B12 level of 200-400 pg/mL borderline, and I usually order a methylmalonic acid level as a follow-up.

How to Treat Vitamin B12 Deficiency in Older Adults

If the blood tests confirm a vitamin B12 deficiency, the doctors will prescribe supplements to get the body’s levels back up. The doctor may also recommend additional tests to find out just why an older person has developed low vitamin B12. 

The usual dosage for initially treating vitamin B12 deficiency in older adults is 1000 micrograms, which can be given as a weekly intramuscular injection, or as a daily oral B12 supplement.

It’s common to start treatment for a significant vitamin B12 deficiency with weekly intramuscular shots (1000 micrograms of vitamin B12). This bypasses any absorption problems in the stomach or intestine, and is a good way to get an older person’s vitamin B12 level back to normal quickly.

High-dose oral vitamin B12 supplements (1000-2000 micrograms per day) have also been shown to raise levels, because high doses can usually compensate for the body’s poor absorption. However, oral treatments probably take longer to work than intramuscular shots. So they’re not ideal for initially correcting a deficiency, although they’re sometimes used to maintain vitamin B12 levels. I go into detail on the two most common oral B12 supplements, Methylcobalamin and Cyanocobalamin, in my Youtube video here:

I’ve found that most older patients prefer oral supplements over regular vitamin B12 injections, which is understandable; shots aren’t fun. However, this requires the older person to consistently take their supplement every single day. If you (or your older relative) has difficulty taking medications regularly, scheduled vitamin B12 shots are often the better option.

And the good thing about vitamin B12 treatment is that it’s basically impossible to overdose. Unlike some other vitamins, vitamin B12 doesn’t cause toxicity when levels are high. 

So if you’re being treated for vitamin B12 deficiency, you don’t need to worry that the doctors will overshoot. You just need to make sure a follow-up test has confirmed better vitamin B12 levels, and then you can work with the doctors to find the right maintenance dose to prevent future vitamin B12 deficiency. 

For an older person on vitamin B12 injections, once the blood level of vitamin B12 has normalized, the injections can be given once a month.

Are There Other Benefits To Taking Vitamin B12 Supplements?

Since we know vitamin B12 is necessary for the proper function of red blood cells and brain cells, you might be wondering if it’s good to take higher doses of vitamin B12 as part of a healthy aging approach.

It certainly won’t hurt, since vitamin B12 doesn’t cause problems at higher blood levels the way some vitamins do.

But once an older person has a good level of vitamin B12 in the body, it’s not clear that additional vitamin B12 will reduce the risk of problems like cancer or dementia. To date, much of the research on the benefits of extra vitamin B12 has been inconclusive. 

However, research has definitely confirmed that a deficiency in this essential vitamin is harmful to the body and the brain, with worse deficiencies generally causing greater harm.

So to help yourself or a loved one make the most of this vitamin, focus on detecting and treating vitamin B12 deficiency. Remember, this common problem is frequently overlooked.

You can help yourself by asking the doctor to check vitamin B12 if you’ve noticed any related symptoms, or by asking for a proactive check if you have any risk factors.

Older adults often have enough health problems to deal with. Let’s make sure to notice the ones that are easily detectable and treatable.

Have you had any challenges related to vitamin B12 deficiency? I’d love hear from you in the comments below.

 

This article was first published in 2015, and was last updated by Dr. K in September 2024.