Vitamin B12 helps your body make red blood cells, maintain nerve health, may boost energy levels, and support a good metabolism (turning food into energy). Some research suggests that people experiencing obesity are more likely to have low B12, which points to a possible link between B12 levels and body weight. However, more research is needed to determine whether taking vitamin B12 when deficient can help with weight management.
Vitamin B12 plays an important role in metabolism by helping your body turn carbohydrates (the main source of energy in the body), fats, and proteins into glucose (a type of sugar) for energy. This supports steady energy levels throughout the day.
Research suggests that people experiencing obesity often have lower B12 levels. In a 2019 study, higher blood B12 levels were associated with lower obesity rates, even after adjusting for age, income, lifestyle, and supplement use. However, available research only shows an association and doesn’t prove that low B12 causes weight gain.
When vitamin B12 levels are low, fatigue and brain fog make it harder to stick with healthy eating and exercise routines.
B12 deficiency symptoms include:
- Fatigue and low energy
- Weakness
- Shortness of breath
- Numbness or tingling in the hands and feet
- Difficulty concentrating
- Irritability
- Loss of balance
While B12 supplements aren’t a proven method for weight loss, they may indirectly support your efforts in several ways:
- Boost energy levels: B12 helps turn the food you eat into usable energy. When your body has enough B12, this process works more efficiently, which can increase your energy levels and motivation to be active.
- Reduce fatigue: Low B12 levels can cause tiredness and sluggishness. Correcting a deficiency often restores energy, making it easier to move more and burn calories throughout the day.
- Support mood and focus: B12 plays a role in brain health. A deficiency may contribute to depression, brain fog, or poor concentration. Adequate B12 can improve mental clarity and mood, which makes it easier to stick to balanced eating habits and exercise routines.
- Improve exercise performance: With better energy and reduced fatigue, you may find it easier to exercise for longer periods or at a higher intensity. This added activity, paired with a balanced diet, can support weight management.
The recommended daily amount of vitamin B12 for most adults is 2.4 micrograms per day. If you have a B12 deficiency, your doctor may suggest a higher dose.
There are several ways to take vitamin B12 supplements or increase your intake, including:
- Food: Animal-based foods, such as meat, fish, like salmon and tuna, dairy products, eggs, and beef liver, are the richest natural sources of B12. You can also get vitamin B12 by consuming cereals, plant-based milks, and nutritional yeast fortified with B12 if you don’t consume animal products. Fortified foods have nutrients, like B12, added rather than being naturally found in the food.
- Oral supplements: B12 supplements are available over the counter in several forms, including tablets, capsules, and sublingual (under-the-tongue) options.
- B12 Injections: For severe deficiencies or absorption problems, doctors may prescribe B12 shots, which deliver the vitamin directly into the bloodstream.
- Nasal sprays and transdermal patches: Nasal sprays and transdermal (skin) patches offer alternative ways to get B12, but are less common for correcting deficiencies.
Taking vitamin B12 is generally safe, especially if you have a deficiency. B12 is a water-soluble vitamin, which means your body doesn’t store large amounts of it and typically removes any excess amounts when you pee.
However, very high doses may cause side effects such as:
B12 can also interact with certain medications, including those used to treat acid reflux, such as Prilosec (omeprazole) and Prevacid (lansoprazole), as well as some diabetes medications, such as metformin. If you’re looking to start injections or take high-dose supplements, consider talking with a doctor first to make sure it’s safe for you.
