Health Benefits of Vitamin B12: A Complete Guide

As a working mom of three littles under six, I move (more like sprint) through life half-asleep. It looks like this: Me, clutching a cup of coffee I’ve microwaved three times, lugging a diaper bag bursting with snacks (none for me, of course), and scratching my head wondering if I actually ate today. With so many responsibilities to juggle, it’s easy to chalk up my constant fatigue, fogginess, and poor focus to the chaos of motherhood. But what if there’s more to it? What if this constant groggy, out-of-it feeling isn’t just mom life, but a sign that something’s missing?

If that sounds all too familiar, vitamin B12 might be the sneaky culprit behind your mom-brain-meets-brain-fog feeling. This vitamin plays a key role in how your body and brain feel, and helps bridge the gap between feeling drained and actually getting stuff done.

In this article, we’ll explore vitamin B12 benefits, what happens if you’re not getting enough, and easy ways to supplement so you can feel more like yourself again (you know, the version that actually remembers where she put her phone, keys, or sanity).

What is vitamin B12?

Growing up in Los Angeles, I’m all too familiar with seeing ads for vitamin B12 shots plastered on every palm-tree-lined street corner, promising a magic boost of energy and focus. From a young age, I had a pretty good idea of what the vitamin B12 buzz was all about, so here’s the scoop. 

Vitamin B12, also known as cobalamin, is an essential nutrient that your body cannot make on its own. That means you’ve got to get it from food or supplements. Vitamin B12 has its hand in many bodily functions—it helps convert food into energy, forms red blood cells, regulates the nervous system, and supports DNA production. 

Vitamin B12 quietly works behind the scenes to keep you energized, mentally sharp, and running as your best self. “This vitamin plays a vital role in nerve cell health and energy metabolism, which is why it gets a lot of attention for energy and focus,” says Trista Best, MPH, RDN, LD, Registered Dietitian and Adjunct Nutrition Professor. So if you’re feeling drained or a bit hazy, it's no wonder B12 often comes under the spotlight—it powers so many essential processes that help you feel like you.

9 benefits of vitamin B12

Vitamin B12 is essential for nourishing both your body and brain, helping you stay sharp and ward off  all-too-familiar brain farts. Here are the top 9 ways vitamin B12 supports your health:

Supports red blood cell production

Vitamin B12 plays a crucial role in the production of healthy red blood cells. These cells carry oxygen throughout your body, and without enough B12, your body can develop megaloblastic anemia—a type of anemia marked by fewer, unusually large, and underdeveloped red blood cells. “Without adequate B12, red blood cells are at risk of becoming misshapen, which results in an inability to carry oxygen, which can lead to anemia, weakness, and fatigue,” says Best. 

‍Symptoms of B12 deficiency go beyond snooze-inducing fatigue and feeling spaced out. You might also experience:

• Heart palpitations
• Paler-than-normal skin
• A swollen, inflamed tongue
• Neurological issues like numbness or tingling in your hands and feet
• Loss of appetite
• Weight loss
• Poor memory
• Depression

In some cases, vitamin B12 deficiency is caused by pernicious anemia, a condition where the body can’t absorb B12 properly due to a lack of intrinsic factor, a protein made in the stomach. This can result from an autoimmune reaction or a thinning of the stomach lining. Symptoms may not appear until your 30s or later. When this happens, you may also start to notice memory blips (wait…did I turn off the oven?), poor appetite, and an overall sluggishness that leaves you craving a serious pick-me-up (double shot of espresso, please).

Involved in DNA synthesis

Vitamin B12 acts as a cofactor (helper molecule) for enzymes involved in DNA synthesis—the process by which new DNA strands are created. DNA carries the genetic instructions for how each cell in the body is built and how it works, so B12 is essential for healthy cell structure and function. B12 also helps produce RNA (another type of genetic material), along with proteins and fats that our body uses for energy and other physiological functions.

Supports energy levels

Vitamin B12 helps convert the food you eat into usable energy. It’s involved in breaking down nutrients and transforming them into fuel that your cells can use to power your day. Erika Gray, PharmD, Chief Medical Officer of ToolBox Genomics explains that your mitochondria (think of them as tiny power plants in your cells) rely on B12 to help produce adenosine triphosphate (ATP), the body’s main energy currency. This process keeps your energy levels up and your body functioning efficiently.

That said, vitamin B12 doesn’t directly give you energy like caffeine might—it simply supports the body’s natural energy-making process. So if you’re feeling sluggish, it might be due to anemia caused by a vitamin B12 deficiency—not because you need a quick energy boost from B12 itself.

Supports bone health

Ever since learning about osteoporosis in women’s health class, I’ve been laser-focused on keeping my bones strong as I age. Osteoporosis is a chronic bone disease that affects one in three women over age 50, and interestingly, this is one of the benefits of vitamin B12 for women. 

Vitamin B12 keeps your bones strong by building new bone cells and supporting bone formation. In fact, low vitamin B12 levels are associated with lower bone mineral density and a higher risk of fractures—yet another reason to make sure you're getting enough.

Enhances brain health and memory

Remember those brain farts I mentioned? They could be tied to low B12 since it’s involved in homocysteine metabolism, a process that affects many systems in the body, including the nervous system. When vitamin B12 levels are low, homocysteine levels rise, and several studies have linked elevated homocysteine to an increased risk of Alzheimer’s disease and dementia. 

One reason may be B12’s role in the production of myelin, the protective sheath of fat and protein that surrounds and insulates nerves, including nerves in the brain and spinal cord. Myelin efficiently transmits electrical signals throughout the nervous system, and without enough vitamin B12, the myelin sheath can weaken and can slow down communication between your nerves. Enter: brain farts, memory loss, and neurological symptoms like tingling and numbness in your extremities.

Healthy skin, hair, and nails

As I get older, I’m low-key obsessed with not looking like the perpetually tired zombie mom. As I mentioned, a symptom of vitamin B12 deficiency is paler-than-normal skin, and that’s because your body isn’t producing enough healthy red blood cells to carry oxygen to your skin, robbing you of that fresh, vibrant glow. In fact, vitamin B12 deficiency is associated with skin hyperpigmentation (patches of dark spots), linear streaks in the nails, and poliosis, a condition where you develop white streaks in your hair. 

Your B12 levels also impact hair and nail health. Vitamin B12 benefits for hair include ensuring that hair follicles get enough oxygen-rich blood, because without it, you might notice slower growth, hair thinning, or even premature graying (*gasp*). And when it comes to nails, low vitamin B12 has been linked to nail hyperpigmentation—discoloration or dark spots that show up in your nail beds.

Improves mood and depression symptoms

If you’re constantly juggling endless to-dos, neverending snack refills, and the occasional Lego landmine ready to trip you up, it’s no wonder you feel hazy, weary, and totally overwhelmed (yep, that’s me—hi!). And let’s be honest, when you’re frazzled and overstimulated, a sour mood isn’t far behind. At least that’s how it goes for me. Here’s how vitamin B12 can help turn things around, if you’re not getting enough.

“B12 is critical for supporting the production of neurotransmitters such as serotonin and dopamine,” says Gray. “These are your body’s key neurotransmitters that support mood and may improve mood disturbances and depression symptoms.” Serotonin and dopamine are often referred to as the “feel-good” hormones because they promote feelings of happiness, pleasure, reward, and motivation. So when your body is circulating enough of these neurotransmitters, it’s easier to feel better—and less like a grumpy mess.

Supports eye health

Vitamin B12 could reduce the risk of age-related macular degeneration, an eye disease that affects vision. “Low B12 levels could lead to demyelination of the optic nerve, leading to blurry vision,” explains Gray. In other words, the protective coating around your optic nerve can get a little frazzled, which puts your vision at risk. The good news? If a deficiency is caught early, it’s usually easy to fix with a bit of B12 TLC.

May prevent birth defects

When I think about a healthy pregnancy, folic acid or folate comes to mind. But vitamin B12 is just as important and often overlooked. It supports the development of the baby’s central nervous system, and not getting enough during pregnancy can lead to serious health issues like poor growth, delays in brain development, and birth defects. This highlights one of the key vitamin B12 benefits for women, especially during pregnancy and breastfeeding, when daily  requirements increase.

How much vitamin B12 do you need?

The amount of vitamin B12 you need depends on your age and life stage. Here are the Recommended Dietary Allowances (RDAs) to help guide you:

Age	Recommended Daily Allowance
Birth to 6 months	0.4 mcg
7 to 12 months	0.5 mcg
1 to 3 years	0.9 mcg
4 to 8 years	1.2 mcg
9 to 13 years	1.8 mcg
14 to 18 years	2.4 mcg
19+ years	2.4 mcg
Pregnant women	2.6 mcg
Breastfeeding women	2.8 mcg

Foods with vitamin B12

Vitamin B12 is exclusively found in animal-based foods so if you’re a die-hard carnivore or hopping on the beefy protein craze, you’re probably getting plenty of B12 in your meals. Some common sources include:

• Beef
• Pork
• Lamb
• Chicken
• Duck
• Turkey
• Organ meats (liver)
• Fish
• Clams
• Oysters
• Eggs
• Milk
• Yogurt
• Cheese 

Since vitamin B12 isn’t naturally found in plant foods, if you’re vegan or follow a strict vegetarian diet, it’s especially important to watch your B12 intake. This usually means relying on supplements or foods fortified with B12, like breakfast cereals, nutritional yeast, or soy milk. 

Because the amount of B12 in fortified foods can vary, if you follow a plant-based diet, it’s a good idea to talk to your doctor about taking a vitamin B12 supplement to make sure you’re covering all your bases.

Vitamin B12 deficiency

If you’re always running on empty, can’t focus no matter how many hours you sleep, or start spotting weird stuff like pale skin or funky-colored nails, it’s time to check in with your healthcare provider. These can be subtle signs that something’s off, like a vitamin B12 deficiency.

“About a year after I went vegan I started feeling like I was living in a cloud. I was often lightheaded, dizzy, and overall fatigued, which made it challenging to do everyday tasks like cook dinner and workout. I started taking a daily vitamin B12 supplement and about 2 weeks later I started noticing improvements in my energy levels and feeling more like myself.” - Tiffany Bruno, MS, RDN

That’s where lab work comes in. Your doctor will order blood tests to see if you’re low on B12 or other nutrients that could be affecting how you feel. For people who might have a B12 deficiency, the first round of tests typically includes a complete blood count (CBC), including vitamin B12 and folate levels. Since folate deficiency can cause similar symptoms, checking both B12 and folate levels can distinguish between the two. And if your bloodwork shows low vitamin B12 levels, it’s important to figure out what’s causing it in the first place.

What causes vitamin B12 deficiency?

• Vegan diet: If you follow a strict vegan or mostly plant-based diet, you may be at risk for vitamin B12 deficiency. That’s because vitamin B12 is only found in animal products. If this is your preferred way of eating, it’s important to make sure you’re getting enough vitamin B12 through supplements or fortified foods.
• Autoimmune-related: Pernicious anemia is an autoimmune condition where your body attacks intrinsic factor, the protein in your stomach required to absorb vitamin B12. Without intrinsic factor, your body can’t effectively absorb or use vitamin B12. 
• Malabsorption: Some health conditions can interfere with your body’s ability to absorb vitamin B12. For example, if you have celiac disease, damage to the intestines from gluten can make it harder to absorb nutrients, including B12. Likewise, if you’ve had gastric bypass surgery or surgery to remove part of your intestines due to Crohn’s disease, your body may be unable to effectively absorb B12. 
• Age: Stomach acid levels naturally decline with age. Since stomach acid works with intrinsic factor to absorb vitamin B12, this drop can make it harder for seniors (age 60+) to get enough. ‍
• Medications: Certain medications like metformin (commonly used for diabetes) or proton pump inhibitors (used for acid reflux) can interfere with your body’s ability to absorb vitamin B12. If you take these regularly, it’s a good idea to get routine blood work to monitor your levels.

At-risk groups

Certain groups of people are more likely to develop a vitamin B12 deficiency. This includes people with diabetes, older adults (who may struggle with nutrition, access to care, or low stomach acid), anyone with digestive issues like celiac or Crohn’s disease, or pregnant or lactating women.  

As someone who’s been either pregnant or breastfeeding for over six years, I know how easy it is to put our own health on the back burner. Not only do our bodies need more B12 during these stages, but we often forget to eat, skip our postnatal supplements, or barely take a moment to slow down and check in with ourselves. If you fall into any one of these at-risk groups, it’s a good idea to stay on top of your bloodwork and talk to your healthcare provider about checking your B12 levels regularly.

Vitamin B12 supplements

Sure, most of our nutrients should come from food, but that’s not always practical. If you have a true deficiency, supplements help fill in the gaps when our diet isn't quite cutting it. Vitamin B12 is widely available as a standalone supplement or as part of a multivitamin, and it comes in many forms—capsules, injections, and sublingual tablets which dissolve under the tongue.

Personally, I’m fascinated by sublingual forms of vitamin B12, not only because it sounds super futuristic, but the way it works is just cool. Instead of going through your digestive system like a regular pill, the tablet melts under your tongue, gets absorbed by the tiny blood vessels in your mouth, and heads straight into your bloodstream. That means potentially faster effects—sharper focus, mental clarity, and enough energy to actually tackle that to-do list.

Sublingual vitamin B12 is a great option if swallowing pills isn’t your thing, like if you have digestive issues, are older (but wiser!) adult, or you simply don’t enjoy taking pills. 

While no one form of B12 is universally recommended, choosing a method that fits easily into your routine can make it a more sustainable habit. Maybe that means taking your supplements while you’re doing your skincare routine or sipping your morning matcha (habit-stack!) If you suspect a vitamin B12 deficiency or are experiencing symptoms, talk to your healthcare provider about the best vitamin form for you. 

Vitamin B12 injections

If you have a severe deficiency, pernicious anemia, or a condition that interferes with vitamin B12 absorption, your doctor might recommend B12 injections. Injection shots are typically given intramuscularly (into the muscle) and are designed to bypass any absorption issues in the digestive tract.

Treatment usually starts with weekly injections and may taper down to monthly doses once your levels stabilize. While injections can be helpful in certain medical cases that make digestive absorption challenging, there’s no solid evidence that injections are more effective than other forms of vitamin B12 for those without malabsorption issues.

Side effects of vitamin B12

While vitamin B12 supplements are generally considered safe, like any supplement, taking excessive amounts can lead to side effects. Although B12 is a water-soluble vitamin and the body typically flushes out any extra through urine, some gets stored in the liver and high doses can still cause uncomfortable reactions.

“B12 is a water-soluble B vitamin, meaning your body will get rid of any excess,” says Gray.  “However, some people may develop a rash or diarrhea if they take too high of a dose.”

The bottom line

Vitamin B12 is essential for overall health, involved in many important functions throughout the body and brain. It keeps you energized, helps you stay sharp (no more brain farts!), and champions strong bones and glossy hair. A B12 deficiency can have you feeling foggy, tired, and just plain blah, but the good news is that it’s easy to fix. Taking vitamin B12 supplements can be an effective way to restore healthy levels and get you back to feeling like your best, most unstoppable self.

Key takeaways

• Vitamin B12 is an essential nutrient that your body cannot produce on its own, so it must be obtained through animal proteins or supplements. 
• Vitamin B12  has its hand in many bodily functions like converting food into energy, forming red blood cells, regulating the nervous system, and supporting mental health. 
• A vitamin B12 deficiency can cause fatigue, brain fog, pale skin, discolored nails, or a strange tingling or numbing sensation in your hands and feet. 
• Vitamin B12 deficiency is easy to treat with oral supplements, sublingual tablets, or intramuscular shots.