Why B Vitamin Deficiencies Lead to Lack of Energy

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There are eight B vitamins, though they often go by names such as niacin, thiamine, pyroxidine and riboflavin. All B vitamins work within the body to convert carbohydrates to energy. The body does not create B vitamins, so people must consume them in foods such as fortified cereals, poultry, shellfish and eggs. While all B vitamins play a role in energy conversion, B12 has the most impact on energy levels.


B vitamins are not only necessary for converting carbohydrates within food to energy; the body also needs B vitamins for DNA synthesis, tissue and cellular repair, cell production and even the production of sex- and stress-related hormones, according to the University of Maryland Medical Center.

Vitamin B12

Vitamin B12 is necessary for red blood cell production, tissue repair and DNA synthesis. Red blood cells contain a protein known as hemoglobin, which carries oxygen to the tissues. B12 deficiencies can lead to a lack of red blood cells known as anemia, causing a lack of oxygen within the body.

B12 and Energy

One of the first signs of B12 deficiency anemia is fatigue and a lack of energy, according to the National Institutes of Health. Oxygen is not only necessary for breathing but for every chemical process within the body. When there is a lack of oxygen within the body, there is a lack of oxygen within the cells. Along with sugar, cells need oxygen for energy. When the cells lack oxygen, they begin to die, and the body begins to reroute existing oxygen to run the essential functions of the body, such as those of the lungs, brain and heart. When anemia is mild, people may notice fatigue and a lack of energy. When B12 deficiency anemia is severe, it can lead to dizziness, lightheadedness and even dementia.


Treatment often depends on the reason for the vitamin B deficiency. In some cases, anemia occurs due to a lack of consumption of foods rich in B vitamins. Physicians will recommend a diet rich in vitamin B foods and vitamin supplements. When deficiency occurs due to malabsorption, such as from Crohn’s disease or celiac disease, people may require long-term or lifelong vitamin B injections, according to National Institutes of Health.


Treatment for B vitamin deficiencies will often reverse the symptoms, including fatigue and lack of energy. B vitamin deficiencies often require testing in specialized labs to diagnose the disorder. People often go long periods without diagnosis because symptoms mimic so many other conditions.