Man holding shoulder muscle in pain with possible B12 deficiency

11 possible signs of vitamin B12 deficiency

Medically reviewed on May 17, 2022 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Table of contents

Vitamin B12 is an essential vitamin that the human body relies on to function. It’s a key player in some of the body’s most vital operations, from forming new red blood cells and producing DNA to regulating nerve function [1]. Vitamin B12 is also important in pregnancy as it is essential for developing multiple fetal organs.

This is part of the reason why getting the right amount of vitamin B12 supplementation every day is so important to overall health and wellness.

Knowing the most common B12 deficiency signs can help you better understand whether to supplement your B12 intake. Below, we’ll discuss 11 possible signs of deficiency to look out for. (Want to get more B12 in your body? Learn more about Everlywell vitamin B12 supplements.)

1. Unexplained fatigue

Unexpected bouts of fatigue or extreme tiredness are a common sign of a vitamin B12 deficiency. This is because of the role the vitamin plays in the production of red blood cells.

The human body relies on red blood cells to transport oxygen from the lungs to tissues throughout the body. In turn, the tissues use that oxygen to make energy and power the muscles. When you ingest enough vitamin B12 every day, the body is able to make the amount of red blood cells needed to power the muscles, which helps prevent feelings of exhaustion.

Additionally, a vitamin B12 deficiency may also lead to other health issues that can result in fatigue, such as megaloblastic anemia. This is a vitamin deficiency anemia that’s characterized by the production of larger than normal red blood cells [2]. Despite their size, these blood cells aren’t healthy enough to carry oxygen to the body’s tissues. They also tend to experience shorter lifespans than healthy red blood cells.

In addition to fatigue, megaloblastic anemia can cause:

  • Dizziness
  • Shortness of breath
  • Weight loss
  • Muscle weakness

2. Muscle cramps and weakness

If a B12 deficiency is preventing the body from producing enough red blood cells to get oxygen to muscle tissues, you may experience associated symptoms, like sporadic muscle cramps or weakness [3].

Aside from a lack of oxygen, these symptoms are also due to vitamin B12’s role in nervous system function, which includes motor and sensory functions.

3. Paresthesia

Like muscle cramping, another potential sign of a B12 deficiency is intense burning or tingling sensations in various parts of the body—a condition known as paresthesia [3].

If you suffer from paresthesia, you may experience tingling or burning sensations in the:

  • Hands
  • Feet
  • Legs

4. Skin discoloration

Noticeable changes to the color of the skin may also indicate a vitamin B12 deficiency. Unusually pale or yellow skin is often the result of underlying health conditions that vitamin B12 typically protects against, such as [4]:

  • Vitamin deficiency anemias – A B12 deficiency can result in blood conditions, like anemia, that are marked by a scarcity of healthy red blood cells. That scarcity can leach the color from the skin.
  • Jaundice – If the body isn’t making healthy red blood cells, they can die off at a faster rate than usual. This can lead to a build-up of a yellowish pigment, known as bilirubin, that’s created when cells break down. A build-up of bilirubin can, in turn, make the skin and the whites of the eyes a yellowish color.

5. Frequent headaches

A vitamin B12 deficiency can cause a range of neurological conditions, from seizures and developmental delays in infants to impaired vision and memory loss in adults [5, 6]. But among the most common of these neurological conditions, in both adults and children, are headaches.

Vitamin B12 absorption is essential for nerve function, so maintaining the proper levels may help ward off the frequent headaches that deficiency can cause.

In fact, in a 2019 study, medical professionals detected lower than average B12 levels in participants who frequently suffered from migraines over participants who did not, suggesting a link between vitamin B12 deficiencies and the presence of migraines [7].

6. Symptoms of depression

Along with physical health, vitamin B12 can also have an impact on your mental health.

This is because the B vitamins, especially B12 and B9 (also known as folic acid), help the brain produce chemicals that allow it function properly [8]. These chemicals can also play a role in your mood. If a lack of vitamin B12 prevents the brain from making these chemicals, you may experience common depressive symptoms, like:

  • Anxiety
  • Irritability
  • Sadness
  • Restlessness

Additionally, a B12 deficiency can:

  • Lead to increased amounts of the amino acid homocysteine, which can make depression worse [9].
  • Present as an array of non-depressive mood disorders, including agitation, confusion, and amnesia [10].

7. Cognitive issues

Vitamin B12, as well as other B vitamins, are immensely crucial to the body’s central nervous system, where they act as coenzymes that spark chemical reactions to help the nervous system function [11].

For that reason, B12 deficiencies are often signaled by:

  • Confusion
  • Difficulty concentrating
  • Difficulty focusing or completing tasks
  • Reduced problem-solving skills

The risks of cognitive impairments that come with a B12 deficiency are most common in older adults. However, the good news is that there’s evidence to suggest that treating a B12 deficiency can improve related cognitive decline [13].

8. Ataxia

A condition known as ataxia is also common in some people with a vitamin B12 deficiency. Ataxia is a neurological disorder that makes previously simple tasks, like coordination or balance, extremely difficult.

Among the detrimental effects of ataxia are:

  • Trouble walking
  • Trouble balancing
  • Slurred speech

9. Gastrointestinal issues

A vitamin B12 deficiency can cause a range of gastrointestinal issues due to the resulting lack of red blood cells [4]. When you don’t have enough red blood cells, the gut can’t receive the amount of oxygen it needs to function properly.

This means you may experience symptoms such as:

  • Bloating
  • Constipation
  • Diarrhea
  • Gas
  • Nausea

However, it’s important to keep in mind that gastrointestinal issues alone may not signal a vitamin B12 deficiency. Food allergies like celiac disease, metabolic imbalances, and/or other health conditions could also be to blame.

10. Oral inflammation

Studies show an association between vitamin B12 deficiencies and a medical condition known as glossitis [14]. Glossitis is characterized by painful swelling or inflammation of the mouth or tongue, which may also take on an extra red hue.

In many cases, glossitis is the result of a B12 deficiency anemia known as pernicious anemia. In fact, one internal medicine study observed glossitis in up to 25% of patients with pernicious anemia [14].

11. Erectile dysfunction

Individuals who suffer from a vitamin B12 deficiency may experience sexual health issues, such as the inability to achieve or maintain an erection [15].

This is because studies have linked vitamin B12 deficiencies to an increase in the amino acid homocysteine. Although homocysteine helps build vital proteins within the body, it first needs B12 and other B vitamins to break it down into two separate substances:

  • Methionine
  • Cysteine

Without B12, homocysteine doesn’t break down properly, and high levels of homocysteine can deplete a person’s ability to perform sexually.

How to increase your B12 intake

One of the best ways to combat a B12 deficiency is to make sure you’re getting the recommended amount of B12. For most people between the ages of 14 and 50, the recommended amount of B12 is 2.4 micrograms (mcg) per day.

Fortunately, vitamin B12 is readily available in many foods. If you’re interested in boosting your B12 levels, consider adding more of these B12-rich foods to your diet:

  • Seafood – Salmon, tuna, and other maritime delicacies, like clams, are a great source of vitamin B12. They’re also rich in healthy omega-3 fatty acids and vital proteins the body needs.
  • Meat – Red meats, as well as organ meats like liver and kidneys, are especially rich in vitamin B12.
  • Dairy products – Dairy products, such as milk and yogurt, can help you supplement the B12 you’ve been missing out on.
  • Eggs – In addition to being a good source of protein, eggs are also high in vitamin B12. Most of the vitamin content is stored in the egg yolk.
  • Fortified cereals – Many foods and drinks are fortified with a range of vitamins, including B12. Cereals are often heavily fortified, making them an easy and delicious way to consume more B12.

If diet alone doesn't provide you with adequate amounts of B12, talk with your healthcare provider about adding B12 supplements to your daily regimen (vitamin B12 supplements from Everlywell are vegan and non-GMO).

Does vitamin B12 give you energy?

Vitamin B12 recommended dosage for older adults

Benefits of vitamin B12 for your hair


1. Vitamin B12 – Health Professional Fact Sheet. National Institutes of Health. URL. Accessed May 17, 2022.

2. Iqbal SP, Kakepoto GN, Iqbal SP. Vitamin B12 deficiency--a major cause of megaloblastic anaemia in patients attending a tertiary care hospital. J Ayub Med Coll Abbottabad. 2009 Jul-Sep;21(3):92-4.

3. Wolffenbuttel BHR, Wouters HJCM, Heiner-Fokkema MR, van der Klauw MM. The Many Faces of Cobalamin (Vitamin B12) Deficiency. Mayo Clin Proc Innov Qual Outcomes. 2019;3(2):200-214. Published 2019 May 27.

4. Vitamin B12 Deficiency. StatPearls [Internet]. URL. Accessed May 17, 2022.

5. Arıcan P, Bozkurt O, Cavusoglu D, Gencpınar P, Haspolat S, Duman O, Olgac Dundar N. Various Neurological Symptoms with Vitamin B12 Deficiency and Posttreatment Evaluation. J Pediatr Neurosci. 2020 Oct-Dec;15(4):365-369.

6. Vitamin B12 or Folate Deficiency Anemia. National Health Service. URL. Accessed May 17, 2022.

7. Togha M, Razeghi Jahromi S, Ghorbani Z, Martami F, Seifishahpar M. Serum Vitamin B12 and Methylmalonic Acid Status in Migraineurs: A Case-Control Study. Headache. 2019 Oct;59(9):1492-1503.

8. Vitamin B-12 and Depression: Are They Related? Mayo Clinic. URL. Accessed May 17, 2022.

9. Sangle P, Sandhu O, Aftab Z, Anthony AT, Khan S. Vitamin B12 Supplementation: Preventing Onset and Improving Prognosis of Depression. Cureus. 2020;12(10):e11169. Published 2020 Oct 26.

10. Tufan AE, Bilici R, Usta G, Erdoğan A. Mood disorder with mixed, psychotic features due to vitamin b12 deficiency in an adolescent: case report. Child Adolesc Psychiatry Ment Health. 2012;6(1):25. Published 2012 Jun 22.

11. Calderón-Ospina CA, Nava-Mesa MO. B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin. CNS Neurosci Ther. 2020;26(1):5-13.

12. Nalder L, Zheng B, Chiandet G, Middleton LT, de Jager CA. Vitamin B12 and Folate Status in Cognitively Healthy Older Adults and Associations with Cognitive Performance. J Nutr Health Aging. 2021;25(3):287-294.

13. Jatoi S, Hafeez A, Riaz SU, Ali A, Ghauri MI, Zehra M. Low Vitamin B12 Levels: An Underestimated Cause Of Minimal Cognitive Impairment And Dementia. Cureus. 2020;12(2):e6976. Published 2020 Feb 13.

14. Kobayashi A, Iwasaki H. Pernicious anemia presenting as glossitis. CMAJ. 2020;192(16):E434.

15. Xu J, Xu Z, Ge N, Wang C, Hu C, Chen Z, Ouyang J, Pei C. Association between folic acid, homocysteine, vitamin B12 and erectile dysfunction-A cross-sectional study. Andrologia. 2021 Dec;53(11):e14234.

Everlywell makes lab testing easy and convenient with at-home collection and digital results in days. Learn More