Vitamin B12 is also known as cobalamin. It’s one of the eight B vitamins. Each one serves a unique purpose in your body.
Specifically, vitamin B12 is involved in nerve functioning, DNA synthesis (creation), and the formation of red blood cells. It also helps transform the food you eat into energy.
Your body does not produce vitamin B12 on its own, so you need to get it from foods or supplements.
Should you take vitamin B12 for fatigue and low energy?
You might have heard that vitamin B12 acts as a remedy for fatigue and low energy levels. Some people may claim that it can provide instant energy and help keep you awake.
But even though vitamin B12 transforms the food you eat into energy that your body can use, evidence of any energy-boosting effects from the vitamin is limited. Vitamin B12 does not give you instant energy nor does it keep you awake after taking it.
A 2021 analysis of research found just one study that explored the link between vitamin B12 and fatigue in people who did not have a B12 deficiency. It suggested that taking vitamin B12 supplements for 8 weeks might mildly improve fatigue symptoms. Yet the authors explained that the study had several limitations and more research is needed.
Vitamin B12 supplementation may have a greater effect on people who have a B12 deficiency.
A 2017 scientific article explains that low energy levels and fatigue are a symptom of vitamin B12 deficiency. This deficiency may also contribute to anemia, a condition that involves a low red blood cell count or a reduced ability of these cells to carry oxygen. Anemia can also cause fatigue and weakness.
Treating a vitamin B12 deficiency and any associated anemia will likely increase your energy levels. The authors of the 2017 article suggest that this may take around 8 weeks.
Only a healthcare professional can help you determine whether you are deficient in vitamin B12 or if your low energy and fatigue are associated with nutritional deficiencies. Doctors will typically use bloodwork from lab tests to make a diagnosis.
Causes and risks of low vitamin B12
A 2015 research review lists these possible causes of low vitamin B12 levels:
- Low dietary intake: Because B12 is found in animal foods, people who eat a vegetarian or vegan diet may not get enough of the vitamin. In addition, people with alcohol use disorder and older adults are more likely to not get enough from their diet.
- Medications: Proton pump inhibitors, oral contraceptives, hormone replacement therapy drugs, histamine H2-receptor antagonists, and diabetes medications such as metformin may affect the absorption of vitamin B12.
- Malabsorption: Some digestive conditions can limit the absorption of vitamin B12 from your gut. This includes small intestinal bacterial overgrowth (SIBO), Crohn’s disease, gastritis, and celiac disease.
- Other factors: Pregnancy, previous stomach surgery, genetics, and certain autoimmune conditions may also affect vitamin B12 levels.
Possible symptoms and risk factors of vitamin B12 deficiency may include:
- red blood cell conditions (anemia)
- issues with red, white, and platelet blood cells (pancytopenia)
- persistent fatigue
- skin sensations like tingling, numbness, or burning (paresthesia)
- erectile dysfunction
- bowel or urinary incontinence
- depression
- a higher chance of Alzheimer’s disease
- episodes of mania (euphoria) and psychosis
Causes and risks of high vitamin B12
It is unlikely that you’ll develop high levels of vitamin B12 through diet alone. Instead, your levels may rise due to:
- taking too many supplements or taking them for too long
- having liver conditions that challenge excretion, like alcoholic liver disease, cirrhosis, or hepatitis
- having kidney disease
A 2021 article notes that too much oral or injected vitamin B12 is not associated with any significant side effects or harm. It may lead to high vitamin B12 levels, but you’ll likely not feel different.
Some people have speculated that high vitamin B12 levels could suggest the possibility of cancer, including leukemia, colon cancer, or breast cancer. But a 2022 review concluded that there is not enough evidence to support this assumption.
