Is It Alzheimer's Disease or Vitamin B12 Deficiency?

As the name suggests, vitamin B12 deficiency is when there is not enough of the B12 vitamin in your body. This can cause a multitude of symptoms, including a cognitive decline.

Senior woman reading vitamin label
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Vitamin B12 and Cognition

The signs of Alzheimer's and other forms of dementia can mirror the symptoms of a vitamin B12 deficiency. It is important to know the difference and be able to detect both in your loved ones. Unlike Alzheimer's, a B12 deficiency can be reversed.

Have you or a loved one experienced these signs of Alzheimer’s recently?

While you could be experiencing these symptoms due to Alzheimer’s or another dementia, it’s also possible that your symptoms could be related to low levels of vitamin B12.

Several studies have been conducted to establish the link between vitamin B12 and Alzheimer’s symptoms. Some associate low B12 levels with both the symptoms of Alzheimer’s and actual atrophy (shrinkage) of the brain.

Other studies have attempted to prove that B12 supplements restored cognitive functioning to previous levels after supplementation.

Vitamin B12 Deficiency Symptoms

In addition to the above symptoms (memory loss, behavior changes, and agitation) which are similar to the symptoms of Alzheimer’s, people with low B12 may also experience the following:

  • Weight loss
  • Fatigue
  • Weakness
  • Constipation
  • Poor balance
  • Tingling or numbness in hands or feet
  • Depression
  • Sore mouth or tongue


Some cases of low B12 vitamin levels are related to other disease conditions, including pernicious anemia, tapeworms, Crohn’s disease, and celiac disease. Other cases are caused by alcoholism or by a poor vegetarian diet that does not provide enough nutrients.

Another risk factor is increased age since B12 absorption can decline as people age.


Diagnosing vitamin B12 deficiency is accomplished by taking a sample of your blood and testing it to determine the level of vitamin B12 in your system.

Normal results are between 200-900 pg/mL (picograms per milliliter). A desirable threshold for elderly adults is between 300 and 350 pg/mL.

When being evaluated for Alzheimer’s or another dementia, in addition to mental status tests and imaging tests, ask for a blood test to evaluate your vitamin B12 level.

Researchers estimate that as many as 1.5% to 15% of the population is deficient in B12 levels. This is especially true of older adults, whose bodies absorb B12 less efficiently than others.


Treatment of low levels of vitamin B12 is quite simple. If your B12 levels are low, you generally will be prescribed a higher dose of the vitamin, either through injections or a B12 supplement you can take by mouth. Your blood levels are then tested regularly and the vitamin dose is adjusted to the appropriate level.


One way to prevent low levels of vitamin B12 is to eat a diet rich in B12. This includes liver, beef, clams, several kinds of fish, fortified cereals and other sources as well.

Some people take an extra dose of vitamin B12, perhaps as part of their daily vitamin or in a supplemental vitamin as a precaution against developing the condition.

Check with your physician to make sure the amount of B12 is appropriate for you. If your B12 levels are not low, your physician may recommend not taking any extra vitamin B12 as extra amounts have not been proven to be beneficial.

Does Supplementation Prevent Alzheimer's?

At this time, there is no conclusive evidence to suggest that vitamin B12 supplementation can prevent Alzheimer's disease from developing. Regardless, research does repeatedly show that good nutrition (including adequate vitamins such as B12) does make a difference in our brain health, and certain foods are also recommended as part of a brain-healthy diet.

A Word From Verywell

A diagnosis is B12 deficiency may be a reversible cause of confusion and behavior changes. In other words, it’s possible that increasing your B12 level can improve or restore your memory and ability to think clearly. It can also resolve the other symptoms you may be experiencing such as fatigue and weakness.

While Alzheimer’s research continues, there currently are few effective long-term treatments and Alzheimer’s is not reversible. A diagnosis of low B12 levels has the potential to be far more responsive to treatment than Alzheimer’s. While symptoms may not completely disappear, it's possible they may notably improve as your B12 levels are adjusted.

Frequently Asked Questions

  • Do fish oil supplements help with Alzheimer's disease?

    There is a lack of evidence that suggests fish oil supplements help with Alzheimer's disease. However, according to one study on 193 adults with Alzheimer's disease, it was found that the participants had less brain atrophy after their usage of fish oil supplements. This may or may not be related to the supplement.

  • Does folic acid help with memory loss?

    Small amounts of folic acid might help with memory loss, but it is not a guaranteed outcome. Further studies need to be performed to determine its effectiveness. What is known is that an excessive amount of folic acid can be dangerous in some people.

  • How is Alzheimer's disease treated?

    Alzheimer's disease is treated using a combination of prescribed medicine and lifestyle changes. These lifestyle changes involve working with a therapist to understand and confront a person's difficulties with the disease. In addition, they will engage in mentally-engaging exercises to strengthen memory and cognitive function.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Bhatti AB, Usman M, Ali F, Satti SA. Vitamin supplementation as an adjuvant treatment for Alzheimer's DiseaseJ Clin Diagn Res. 2016;10(8):OE07-OE11. doi:10.7860/JCDR/2016/20273.8261

  2. Kim J, Kim MJ, Kho HS. Oral manifestations in vitamin B12 deficiency patients with or without history of gastrectomyBMC Oral Health. 2016;16(1):60. doi:10.1186/s12903-016-0215-y

  3. Green R, Allen LH, Bjørke-Monsen AL, et al. Vitamin B12 deficiency. Nat Rev Dis Primers. 2017;3:17054. doi:10.1038/nrdp.2017.40

  4. Hanna S, Lachover L, Rajarethinam RP. Vitamin b₁₂ deficiency and depression in the elderly: review and case reportPrim Care Companion J Clin Psychiatry. 2009;11(5):269–270. doi:10.4088/PCC.08l00707

  5. Office of Dietary Supplements. National Institutes of Health. Dietary Supplement Fact Sheet: Vitamin B12.

  6. Dauncey MJ. New insights into nutrition and cognitive neuroscience. Proc Nutr Soc. 2009;68(4):408-15. doi:10.1017/S0029665109990188

  7. Daiello, Lori A et al. Association of fish oil supplement use with preservation of brain volume and cognitive function. Alzheimer's & dementia: the journal of the Alzheimer's Association. 2015;11(2):226-35. doi:10.1016/j.jalz.2014.02.005

  8. Selhub J, Rosenberg IH. Excessive folic acid intake and relation to adverse health outcome. Biochimie. 2016;126:71-8. doi:10.1016/j.biochi.2016.04.010

By Esther Heerema, MSW
Esther Heerema, MSW, shares practical tips gained from working with hundreds of people whose lives are touched by Alzheimer's disease and other kinds of dementia.