Glass container with capsules of B vitamin supplements that can help address vitamin B deficiency

Vitamin B Deficiency: Causes and Symptoms

Updated November 29, 2023. Medically reviewed by Neka Miller, PhD. Written by Jordana White. 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

Nutrition tip: make sure you’re getting enough B vitamins because they’re so important to many aspects of your health and well-being. Vitamin B benefits the body by maintaining the health of cells and nerves as well as aiding in the production of DNA.

Read on to learn more about B vitamins: what they can mean for your health, symptoms and causes of deficiency, and more.

What Is Vitamin B?

Vitamin B refers to several different types of vitamins that, together, are known as the B-complex vitamins. Vitamin B benefits the nerves and cells within the body and also helps with the production of DNA (the chemical substance that genes are made from).

There are 8 kinds of vitamins in the vitamin B complex: thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine B6, biotin (B7), folate (B9, also known as folic acid), and cobalamin (B12). Deficiencies in these B vitamins can lead to a number of different symptoms over time (if the deficiency isn’t reversed).

Each of these eight B vitamins play important roles in the body. B vitamins are needed to drive the chemical reactions that support your body’s many functions. For example, cells use B vitamins to generate energy from sugar, fatty acids, and other nutrients. So without B-complex vitamins, the human body could not function well at all.

B vitamins are water-soluble vitamins. [1] In other words, they can dissolve in water – so excess B vitamins your body doesn’t use are washed out through urination, for example.

Benefits of B Vitamins

Benefits of Vitamin B6

  • Helps the body build neurotransmitters (like dopamine), which are special chemicals your brain needs to function
  • Helps your body make red blood cells
  • Helps immune system antibodies work correctly
  • May help lower the risk of lung cancer (though more research is needed to firmly establish this benefit of B6)

Benefits of Vitamin B9 (Folate or Folic Acid)

  • Helps the body make and repair DNA (genetic material)
  • Helps your body make red blood cells
  • Supplementing with high-enough levels of B9 before pregnancy (as well as during pregnancy) significantly lowers the risk of giving birth to a baby with neural tube defects like spina bifida

Benefits of Vitamin B12

  • Helps the body make and repair DNA (genetic material)
  • Helps your body make red blood cells – as well as nerve cells
  • Helps support healthy hair, skin, and nails

Vitamin B12 can affect your red blood cell count, and can even lead to neurological symptoms in severe cases. [2] If someone’s vitamin B12 status isn’t at a normal level, their healthcare provider may recommend a high-dosage B12 supplement or even—in some cases—B12 injections.

B Vitamin Deficiency: Symptoms and Causes of Low Vitamin B Levels

When it comes to vitamins needed for both a sound body and mind, the B vitamins aren’t something you want to ignore. Take, for example, vitamin B12: don’t get enough of this vitamin, and your energy levels throughout the day might sag – with your mind constantly turning, perhaps, to thoughts of sleep in your warm cozy bed.

Or consider vitamin B9 (a.k.a. folate or folic acid): a deficiency in this vitamin and you might get sores on your mouth or a swollen tongue – among other possible symptoms.

Then there’s vitamin B6. If your levels of this key B vitamin are too low, then you could be looking at flaky, oily rashes on your upper body or face.

But these aren’t the only symptoms of B vitamin deficiency. So here’s a more complete list of vitamin B deficiency symptoms.

Other Signs and Symptoms of a B Vitamin Deficiency

Vitamin B6 Deficiency

Signs of B6 deficiency include:

  • Getting sick from infections more often (because B6 helps support your immune system)
  • Getting cracks or sores in the skin around the corners of your mouth – or a swollen and sensitive tongue
  • Fatigue
  • A feeling of numbness or tingling in your hands and feet (this is known as “paresthesias”)
  • Depression, anxiety, and/or irritability
  • A red, itchy rash – often oily or flaky – that usually appears on the upper body or face. Small areas of your skin might also swell, resulting in white patches
  • Convulsions
  • Decreased alertness

Vitamin B9 Deficiency

Signs of B9 deficiency include:

  • Fatigue
  • More gray hair
  • Mouth sores
  • A swollen tongue
  • Weakness
  • Shortness of breath
  • Pale skin
  • Irritability

Vitamin B12 Deficiency

Signs of B12 deficiency include:

  • A feeling of numbness or tingling in your hands and feet (or “paresthesias”)
  • A smooth-appearing tongue
  • Fatigue
  • Weakness
  • Mouth sores
  • Mood changes
  • Blurry vision
  • Loss of breath
  • Dizziness
  • Pale skin

Vitamin B Deficiency Diseases and Conditions

Vitamin B deficiency can increase the risk of various diseases and conditions which can affect your heart health, brain health, mental well-being, and more. For example, both B9 and B12 deficiency causes anemia in some cases – a condition in which your body lacks healthy red blood cells (which makes it hard for different parts of your body to get the oxygen they need). Anemia can also lead to fatigue, dizziness, shortness of breath, and even numbness and tingling in some cases.

Other conditions linked with vitamin B deficiency include:

  • Paresthesias – A “pins-and-needles” feeling often experienced around the arms, hands, legs, or feet
  • Peripheral neuropathy – A nervous system condition that is often felt as a stabbing or burning pain
  • Psychosis – A mental condition in which one’s thoughts and perceptions are significantly altered, resulting in delusions, hallucinations, nonsense speech, or other symptoms
  • Heart attack and stroke – A deficiency in vitamin B12 may heighten the risk of getting a heart attack or stroke

What Causes Vitamin B Deficiency?

Here’s a roundup of 4 of the top causes of vitamin B deficiency: a non-balanced diet, excessive alcohol consumption, various medications (such as proton-pump inhibitors, or PPIs), and gut malabsorption conditions.

(1) A Non-Balanced Diet

Your body can’t directly make B vitamins (unlike proteins, for example – which the body manufactures out of many smaller building blocks).

But that’s usually not a problem because your body gets B vitamins from the food you eat. If you follow a well-balanced diet that provides your body with the right level of nutrients, you can help avoid symptoms of vitamin B deficiencies.

However, for a variety of reasons, sometimes we don’t eat the right balance of food necessary to get enough of the vitamins we need. (For example, if you follow a vegan or vegetarian diet, then you might not get enough vitamin B12 – because vitamin B12 is found almost exclusively in animal-based foods and dairy products. [3])

That’s when vitamin deficiencies – like vitamin B deficiency – can crop up. As such, dietary inadequacies are one of the key causes of vitamin B deficiency.

So, obvious follow-up question here: what foods contain a lot of B vitamins? Well, that depends on which B vitamin is under consideration – vitamin B6, B9, or B12. Here’s a quick rundown of foods you can eat to boost your levels of each of these B vitamins [4-6]:

  • Vitamin B6 – Meat, fish, legumes, nuts, bananas, potatoes
  • Vitamin B9 – Leafy vegetables, legumes, citrus fruits
  • Vitamin B12 – Meat, fish, and other animal and dairy products

(2) Excessive Alcohol Consumption

Whether your drink of choice is shaken and not stirred, includes a barrel-aged spirit, or is a humble mug of beer, there’s nothing especially harmful about (safely) having a drink every now and then.

Needless to say, though, excessive alcohol consumption can have its downsides – one of which is vitamin B deficiency. Alcohol, in short, makes your kidneys flush B vitamins out of your system much more quickly than usual. That means your body doesn’t have all the time it needs to make use of these B vitamins – so they, quite literally, go to waste.

(3) Certain Medications

Several types of prescription medicines can bump up the likelihood of a vitamin B deficiency:

  • Increased likelihood of vitamin B6 deficiency – anticonvulsants, isoniazid, hydralazine, corticosteroids, and penicillamine (common brand name: Cuprimine)
  • Increased likelihood of vitamin B9 deficiency – phenytoin (common brand name: Dilantin), trimethoprim-sulfamethoxazole, methotrexate (common brand names: Rheumatrex, Trexall), and sulfasalazine (common brand name: Azulfidine)
  • Increased likelihood of vitamin B12 deficiency – metformin, proton pump inhibitors (PPIs), antacids, long-term antibiotics, and antidepressants

(4) Gut Malabsorption Conditions

Under healthy conditions, B vitamins are absorbed by the gut and into your bloodstream. The bloodstream then transports these much-needed vitamins throughout your body. So what happens if B vitamins don’t make it into the bloodstream? It’s simple: they can’t be put to good use by the body!

And that’s exactly what can go wrong if you have a gut malabsorption condition – like Crohn’s, for example, or ulcerative colitis or Celiac disease. These conditions prevent B vitamins from entering the bloodstream, significantly dropping your blood’s vitamin B levels – and potentially harming your well-being.


Since vitamin B deficiency is relatively common – some have even declared it a “worldwide problem” [7] – it’s helpful to know some of its main causes (like the 4 described above).

It’s recommended that older adults who have deficient levels of vitamin B talk with their healthcare provider as soon as possible to come up with a treatment plan. If you are showing vitamin B deficiency symptoms, it may be because you do not have enough vitamin B in your diet. If you're showing signs of tiredness, lightheadedness, shortness of breath, or other deficiency symptoms, consider checking your B vitamins level. For those looking to improve their vitamin B levels, Everlywell offers vegan, non-GMO vitamin B12 and B6 supplements.

11 Possible Signs of Vitamin B12 Deficiency

How Long Does It Take to Recover From Vitamin B12 Deficiency?

Symptoms of Low Vitamin D: What Are the Signs of Vitamin D Deficiency?


  1. Lykstad J, Sharma S. Biochemistry, Water Soluble Vitamins. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2020.
  2. Kennedy DO. B Vitamins and the Brain: Mechanisms, Dose and Efficacy--A Review. Nutrients. 2016;8(2):68. doi:10.3390/nu8020068
  3. Rizzo G, Laganà AS, Rapisarda AM, et al. Vitamin B12 among Vegetarians: Status, Assessment and Supplementation. Nutrients. 2016;8(12):767. Published 2016 Nov 29. doi:10.3390/nu8120767
  4. Vitamin B6. National Institutes of Health - Office of Dietary Supplements. Accessed November 29, 2023. Updated June 16, 2023.
  5. Folate. National Institutes of Health - Office of Dietary Supplements. Accessed November 29, 2023. Updated November 1, 2022.
  6. Vitamin B12. National Institutes of Health - Office of Dietary Supplements. Accessed November 29, 2023. Updated July 7, 2021.
  7. Stabler SP, Allen RH. Vitamin B12 deficiency as a worldwide problem. Annu Rev Nutr. 2004;24:299-326. doi:10.1146/annurev.nutr.24.012003.132440

Originally published February 6, 2019.

Neka Miller, PhD holds a PhD in Molecular Pharmacology and is an experienced technical writer covering topics including pharmacology, cancer initiation, neuroscience, and traumatic brain injury. Miller has also created manuals and custom reports featuring data visualizations, protocols, method sections, and manuscripts, as well as authoring published works in scientific journals.

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