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Does vitamin B12 give you energy?

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Vitamin B12 for fatigueLow B12 causes and risksHigh B12 causes and risksNatural sourcesSupplementsHow to manage high levelsSummary
If you have a vitamin B12 deficiency, vitamin B12 supplements or injections may help reduce fatigue. But current evidence does not suggest that vitamin B12 supplementation improves energy levels in people without a deficiency.
Medically reviewed by Amy Richter, RD
Updated on

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?

Vitamin B12 vials for injections for low energy
Yevhenii Khil/Getty Images

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.

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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. 

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Natural sources of vitamin B12

You can get vitamin B12 from animal-based foods like:

  • meat and poultry
  • fish
  • dairy products
  • eggs
  • seafood

In addition, some non-animal foods are fortified with vitamin B12, including: 

  • nutritional yeast 
  • breakfast cereals
  • plant-based milk
  • meat substitutes

When to take a supplement

The 2015 review referenced earlier notes that you can manage vitamin B12 deficiency with oral B12 supplements or intramuscular injections when treating pernicious anemia.

Oral supplements come in different forms, such as:

  • gummies
  • nasal sprays
  • pills
  • sublingual tablets and drops
  • liquids

A healthcare professional may advise whether vitamin B12 supplements are right for you and, if so, which ones to consider. They can also let you know the right dosage and treatment duration.

Common B12 supplements include: 

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How to manage high vitamin B12

An older 2013 study defines high vitamin B12 levels as those above 950 picograms per milliliter (pg/mL), or 701 picomoles per liter (pmol/L). 

As mentioned, high levels may not cause any symptoms nor need treatment. Still, the 2013 study emphasizes that elevated levels could be a sign of other health conditions, like liver and kidney disease. 

A healthcare professional may want to perform any necessary tests and can recommend suitable treatment if required. 


If you have a vitamin B12 deficiency, taking vitamin B12 supplements might increase your energy levels. Otherwise, these supplements are unlikely to reduce fatigue.

If you are concerned about your B12 levels or fatigue, you may wish to consult a healthcare professional to determine the best approach for diagnosis and treatment. 

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