Vitamin B12 Benefits: What It Does for Energy, Brain and Body

Vitamin B12 helps your body make healthy red blood cells, keeps your brain and nerves working, and is needed to make DNA. It also plays a part in turning food into energy. Most adults need 2.4 mcg a day, and the benefits are clearest for people whose levels are low. (NIH ODS; Tardy and colleagues, 2020) This guide explains what B12 does, whether it gives you energy, who is most likely to run low, how much you need, and what B12 means for women and men.

It is educational, not medical advice.

Key Takeaways

• Three core jobs: B12 is needed for red blood cell formation, DNA synthesis, and the development and function of the brain and nerves (NIH ODS).
• Part of energy metabolism: B vitamins including B12 are involved in the body's energy-yielding metabolism, and tiredness can appear when B12 status is not adequate (Tardy and colleagues, 2020).
• Low levels are common: about 3.6% of US adults have B12 deficiency and about 12.5% have insufficient levels (NIH ODS).
• Small daily need: adults need 2.4 mcg a day, a little more during pregnancy (2.6 mcg) and breastfeeding (2.8 mcg) (NIH ODS).

What Is Vitamin B12?

Vitamin B12, also called cobalamin, is a water-soluble B vitamin. It works as a helper (cofactor) for two enzymes: methionine synthase turns homocysteine into the amino acid methionine, which the body uses to make its main methyl donor, and L-methylmalonyl-CoA mutase converts L-methylmalonyl-CoA to succinyl-CoA (NIH ODS). Natural food sources of B12 are limited to animal foods such as meat, fish, eggs and dairy, which is why fortified foods and supplements matter for people who eat few or no animal foods (NIH ODS). Our guide to vitamin B12 foods lists the best sources.

5 Benefits of Vitamin B12

1. Healthy red blood cells

Your body needs B12 to form healthy red blood cells, which carry oxygen around the body (NIH ODS). When B12 runs low, red blood cells can come out large and abnormal, one reason low B12 can leave you pale and tired (NIH ODS).

2. Brain and nerve function

B12 is required for the development, myelination and function of the central nervous system (NIH ODS). Myelin is the protective coating around nerves. Together, the B vitamins, including B12, support brain functions such as energy production, DNA repair, methylation and making the chemical messengers nerve cells use (Kennedy, 2016).

3. Energy metabolism

B12 plays a role in cellular metabolism, including mitochondrial metabolism, the process cells use to make energy (Green and colleagues, 2017). B vitamins including B12 are part of energy-yielding metabolism, which supports both brain and muscle function (Tardy and colleagues, 2020).

4. DNA and methylation

Every new cell needs DNA, and making it depends on B12 (NIH ODS). B12 is also central to methylation, a chemical process the body uses to switch genes on and off and to make many compounds (Green and colleagues, 2017).

5. Meeting higher needs in pregnancy and breastfeeding

Needs rise from 2.4 mcg a day to 2.6 mcg during pregnancy and 2.8 mcg while breastfeeding, because the baby relies on B12 from the mother during development (NIH ODS). Anyone pregnant or breastfeeding should check supplements with their doctor.

Does B12 Give You Energy?

B12 supports energy by helping your cells turn food into usable energy (Tardy and colleagues, 2020). Fatigue is a recognised sign of low B12, so people whose levels are low often notice the biggest difference once their levels are back in a healthy range (NIH ODS). B12 is often promoted as an energy booster, and its effect on energy and endurance shows up most clearly in people who are not getting enough (NIH ODS). If you feel tired all the time, a blood test is the quickest way to know whether B12 is part of the picture. Our guides to vitamins for energy and waking up when you are tired cover other common causes.

Signs Your B12 May Be Low

• Tiredness and low energy (NIH ODS)
• Numbness or tingling in the hands and feet, which can appear even without changes in the blood count (NIH ODS)
• Pale skin, a fast heartbeat or a sore tongue (NIH ODS)
• Slow onset: symptoms can take several years to appear (NIH ODS)

Who Is Most Likely to Run Low?

• Older adults: between 3% and 43% of older adults living in the community have low B12, often because the stomach makes less of the acid needed to free B12 from food (NIH ODS).
• Vegans and vegetarians: natural B12 sources are limited to animal foods, so plant-based eaters have a higher risk (NIH ODS).
• People who have had stomach or bowel surgery, including weight loss surgery (NIH ODS).
• People on some long-term medicines that lower stomach acid or blood sugar; see the doctor section below (NIH ODS).

Low levels without obvious symptoms are more common than full deficiency, affecting between 2.5% and 26% of people depending on how it is defined (Green and colleagues, 2017).

B12 Benefits for Women and Men

B12 does the same jobs in everyone, and adult men and women have the same daily need. The differences come with life stage and diet (NIH ODS).

Group	Daily B12 need (RDA)	What to know
Adult men (19+)	2.4 mcg	Needs stay the same with age, but absorption from food can fall later in life
Adult women (19+)	2.4 mcg	Same as men outside pregnancy and breastfeeding
Pregnancy	2.6 mcg	Needs rise because the baby relies on B12 from the mother
Breastfeeding	2.8 mcg	The highest adult need
Vegans and vegetarians	2.4 mcg	Need fortified foods or a supplement to reach it

Source for the table: (NIH ODS).

How Much B12 Do You Need, and Can You Take Too Much?

Adults need 2.4 mcg a day (NIH ODS). No upper limit has been set for B12 because it has a low potential for toxicity and is generally considered safe even at high doses (NIH ODS). B12 comes in several forms; our guide to methylcobalamin vs cyanocobalamin compares them, and our B12 nasal spray guide covers sprays, shots and dosage. If you are choosing between two natural forms, our guide to methylcobalamin vs hydroxocobalamin explains how they differ.

For safe amounts, how much of a high dose is absorbed and what a high B12 blood test means, see can you take too much B12.

Wondering when to take it? Our guide to the best time to take B12 covers morning or night and with or without food.

Where Our B12 Fits

Our Methyl B-12 Nasal Spray provides 408 mcg of vitamin B12 as methylcobalamin per two-spray serving, used once a day. We chose methylcobalamin because it is the natural, bioidentical form. The Energy Stack pairs it with NAD+ Nasal Spray and Forage in one daily routine. Learn more on our methyl B12 ingredient page and on our non-stimulant energy and focus hub. Talk to your doctor before starting a supplement if you are pregnant, breastfeeding or take medication.

When to See a Doctor

See a doctor if you have ongoing tiredness, numbness or tingling in your hands or feet, a sore tongue, memory problems or trouble with balance. These can be signs of low B12 or megaloblastic anemia, which can come from pernicious anemia, digestive conditions, stomach surgery, a vegan diet or long-term use of medicines such as metformin or acid reducers (proton pump inhibitors and H2 blockers) (NIH ODS). A blood test can check your level, and nerve symptoms should be checked early. If your doctor prescribes B12, follow their advice on the form and dose.

Frequently Asked Questions

What are the main benefits of vitamin B12?

B12 supports red blood cell formation, brain and nerve function and DNA synthesis (NIH ODS), and it is part of the body's energy-yielding metabolism (Tardy and colleagues, 2020).

Does B12 give you energy?

B12 helps cells turn food into energy (Tardy and colleagues, 2020). People who are low usually notice the biggest change, because tiredness is a recognised sign of low B12 (NIH ODS).

What are the benefits of B12 for women?

The same as for men, plus a higher need during pregnancy (2.6 mcg) and breastfeeding (2.8 mcg) (NIH ODS).

What are the benefits of B12 for men?

Healthy red blood cells, nerve function and energy metabolism, with a daily need of 2.4 mcg (NIH ODS).

How much B12 should I take a day?

Adults need 2.4 mcg a day from food and supplements combined (NIH ODS). Supplements often contain much more, which is considered safe because B12 has a low potential for toxicity (NIH ODS).

Can you take too much B12?

No upper limit has been set, and B12 is generally considered safe even at high doses (NIH ODS).

Who should take a B12 supplement?

Vegans and vegetarians, many older adults, people who have had stomach or bowel surgery and people on certain long-term medicines are most likely to benefit (NIH ODS).

Which form of B12 is best?

Methylcobalamin and cyanocobalamin both raise B12 levels; our B12 forms guide explains the differences.

Sources

• NIH Office of Dietary Supplements. Vitamin B12: Fact Sheet for Health Professionals. NIH ODS
• Tardy AL, Pouteau E, Marquez D, et al. Vitamins and minerals for energy, fatigue and cognition: a narrative review of the biochemical and clinical evidence. Nutrients. 2020. PubMed 31963141
• Kennedy DO. B vitamins and the brain: mechanisms, dose and efficacy, a review. Nutrients. 2016. PubMed 26828517
• Green R, Allen LH, Bjørke-Monsen AL, et al. Vitamin B12 deficiency. Nat Rev Dis Primers. 2017. PubMed 28660890

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.