Vitamin B12

Effect on Fatigue

By Charles Li, MD

Introduction: Vitamin B12 and Fatigue

Vitamin B12 plays an important role in your mental and physical health.

It is a key nutrient for keeping your blood cells and your neurons happy and healthy.

B12 Key Facts

While Vitamin B12 itself doesn’t give you energy, the red blood cells that required it to survive can affect your feelings of fatigue.

Anemia, a condition where you don’t have enough red blood cells carrying oxygen to your tissues, often presents itself as fatigue.

Expert Opinion
Vitamin B12 and Anemia

"Vitamin B12 or folate deficiency anaemia can cause a wide range of symptoms. These usually develop gradually, but can worsen if the condition goes untreated. Anaemia is where you have fewer red blood cells than normal or you have an abnormally low amount of a substance called haemoglobin in each red blood cell."


Fatigue as a Symptom

As a result, fatigue is one of the most common symptoms seen by doctors and patients who don’t have enough vitamin B12. In effect, doctors are watching for signs of not having healthy red blood cells.

Deficiency Symptoms
5 Symptoms
Extreme Tiredness
Feels like fatigue or lethargy. A lack of energy.
B12 deficiency can manifest itself as muscle weakness.
Loss of appetite
You don't feel like eating things like you used to love eating.
B12 deficiency can lead to problems in your digestive system, including difficulty pooping.
Numbness and tingling
B12 deficiency can lead to numbness and a sensation of "pins and needles"

Vitamin B12 Deficiency Prevalence

This is significant because Vitamin B12 deficiency tends to be pretty common.

While estimates can be a little all over the map, it’s generally believed that around 1-1.5% of Americans have low Vitamin B12.

The elderly, who are at risk of having digestive issues that prevent them from absorbing enough Vitamin B12, tend to have higher rates of B12 deficiency.

Pregnant women have the highest risk of not having enough Vitamin B12.

Key Facts
Vitamin B12 Deficiency
Deficiency Rate
Studies estimate that 1.5-15% of the general population has a B12 deficiency
Among Elderly
Generally, studies have found that elderly individuals are at higher risk.
Pregnant Women
30-60% of pregnant women have Vitamin B12 deficiency
Studies estimate that 1.5-15% of the general population has a B12 deficiency. Generally, studies have found that elderly individuals are at higher risk. 30-60% of pregnant women have Vitamin B12 deficiency.

Vitamin B12 and Chronic Fatigue

Vitamin B12 deficiency is a condition that doctors can test for pretty easily.

A blood test can tell you whether you have enough Vitamin B12 or not.

Given how common B12 deficiency is, it can be a useful thing to rule out as a cause of fatigue since if B12 deficiency is indeed causing your fatigue, it is treatable with B12 supplementation.

However, it’s important to note that there is no evidence that people who have enough B12 will benefit from getting more Vitamin B12.