Does Vitamin B12 Deficiency Lead To Weight Gain? What You Should Know

Reviewed By Madhu Sharma , Registered Dietitian, RD, Registered Dietitian
Written by Priyanka Sadhukhan , MSc (Nutrition), Certified Diabetes Educator

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a key role in the normal functioning of the brain and nervous system. Vitamin B12 is involved in the formation of blood cells, DNA synthesis, and energy production (1). The deficiency of vitamin B12 is characterized by anemia, nervous disorder, and low energy levels (2).

People often blame vitamin B12 deficiency for their weight gain. This article helps you find out the truth scientifically – whether vitamin B12 deficiency and weight gain are related or not.

Symptoms of Vitamin B12 Deficiency

When there is a deficiency of vitamin B12, cell division slows down. Due to this slow cell division, red blood cells are enlarged and destroyed by the immune system. There are several symptoms of Vitamin B12 deficiency (3), (4). They are:

  1. 1. Chronic Fatigue – Vitamin B12 deficiency can cause a persistent feeling of exhaustion and tiredness.
  2. Incontinence – Due to vitamin B12 deficiency, the bladder is incapable of holding urine, and leakage occurs.
  3. Shortness Of Breath – Shortness of breath or slow breathing is mainly caused due to B12 not being properly absorbed by the body.
  4. Forgetfulness – Forgetfulness is a common symptom that occurs when the neurological system is deprived of vitamin B12.
  5. Hallucinations And Psychosis – Extreme symptoms that can occur due to vitamin B12 deficiency are hallucinations and weak mental conditions.

Does Vitamin B12 Lead To Weight Gain Or Weight Loss?

There is very little evidence to suggest that vitamin B12 leads to weight gain or weight loss.

Studies associate low vitamin B12 levels with obesity. However, people with a normal BMI range showed a negative correlation with vitamin B12 (5). Another study associated obesity in children and adolescents with an increased risk of low vitamin B12 levels (6).

A recent study on US population shows that high serum vitamin B12 levels are inversely proportional to body weight, but the underlying mechanism needs further investigation (7).

A study in NewYork states that long-term supplementation with vitamin B12 can lead to less weight gain (8). However, more studies are required to arrive at a conclusion.

A 15-year-old boy with macrocytic anemia and other clinical conditions, when supplemented with intravenous cobalamin, showed an increase in appetite and weight (9).

It is pretty clear that current evidence is inconclusive to establish that vitamin B12 deficiency leads to weight gain. However, low vitamin B12 levels are observed among people with obesity issues.

If you are experiencing any of the vitamin B12 deficiency symptoms and weight changes, scroll down to see what the best sources of vitamin B12  are that you can include in your meals.

How To Get More Vitamin B12?

The best and natural way to get vitamin B12 in your body is to eat foods that contain it. Foods rich in vitamin B12 include (4):

  • Meat and chicken
  • Seafood
  • Eggs
  • Dairy and dairy products
  • Fortified breakfast cereals

Apart from these natural sources, you can also take vitamin B12 capsules, syrups, and health drinks that can help bring your vitamin B12 levels back to normal. But before taking any supplements or medicines, make sure to consult the doctor.


Vitamin B12 deficiency is more common among vegetarians as protein affects its absorption. But there is very little evidence to link vitamin B12 deficiency and weight gain. In fact, people with high BMI sometimes have low levels of vitamin B12. If you notice unexpected weight gain, please check with the doctor or a healthcare professional to determine the cause.

Frequently Asked Questions

Can low vitamin B12 make you tired?

As vitamin B12 is required to operate biochemical reactions for energy production, low levels of B12 cause you to feel tired because of lack of energy production.

Can low vitamin B12 cause anxiety?

Vitamin B12 regulates functions of the nerves. Hence, low B12 levels may cause psychiatric symptoms like depression, anxiety, as well as hallucinations.

What is the difference between vitamin B12 deficiency and anemia?

There is no difference between B12 deficiency and anemia. In fact, vitamin B12 deficiency leads to anemia as it regulates functions of red blood cells.


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Madhu Sharma

(Registered Dietitian, RD)
Madhu Sharma is a member of the National Executive Committee of IDA. She has been associated for almost three decades... more