B12 Deficiency: Who’s at Risk and How to Fix It
Written by
Brenda Peralta, RDN, CDEYou might start noticing that you feel tired more often. Or maybe you have memory slips here and there. It might be that your hands and feet tingle once in a while. It’s easy to blame age, stress, or a busy schedule.
However, sometimes, the cause might be a nutrient deficiency. Low vitamin B12 is more common than most people think, especially after 50, and its symptoms are easy to mistake for normal aging.
Because your liver holds most of your vitamin B12 reserves, it can take years to notice low vitamin B12 levels. So, by the time you feel tired, foggy, or your hands and feet are numb, the deficiency might have been building up for a while.
But vitamin B12 deficiency is both treatable and preventable. Here, we’ll take a look at why vitamin B12 matters, who’s most likely to run low, the symptoms to watch out for, and the treatment options you have available to fix it.
Key takeaways · Updated November 11, 2026
- B12 deficiency is more common than many realize, particularly among older adults, vegans, vegetarians, people with digestive issues, and those taking certain medications (like metformin or acid reducers).
- Symptoms can be subtle and might take some time to appear. Common symptoms include fatigue, brain fog, tingling in the hands and feet, and mood changes.
- A standard blood test can detect early deficiency before your levels drop significantly.
- Treating vitamin B12 deficiency involves making dietary changes, taking oral supplements, or taking B12 injections to help improve its absorption.
Why is vitamin B12 important?
B12 helps your body in 2 main ways: it keeps your blood and nerve cells working properly, and it helps make DNA (the genetic material in every cell).
When there is not enough B12, your body struggles to produce healthy red blood cells, which can lead to a condition known as megaloblastic anemia. This type of anemia makes you feel tired and weak because your blood can’t carry oxygen as efficiently as it should.
B12 also helps support your nervous system. A long-term deficiency can lead to nerve damage over time, even before the anemia shows up in your bloodwork. That’s why it’s important to catch a deficiency early.
The recommended intake for vitamin B12 is 2.4–2.8 mcg for adults. However, pregnant and breastfeeding women might need slightly more. While most people can get this through food, some groups might fall short and increase their risk of a deficiency.
Who’s at risk for B12 deficiency?
Getting enough vitamin B12 is just part of it. Your body also needs to absorb it properly, and several factors can affect that process. Here are some people at higher risk of vitamin B12 deficiency, either because of low vitamin B12 intake or poor absorption.
Older adults with reduced stomach acid production
To absorb vitamin B12, the stomach acids need to separate B12 from the protein it’s attached to. Then, B12 binds to a protein called intrinsic factor (made in your stomach) so your body can then absorb it.
As people age, stomach acid production is often reduced, making this first step harder to complete. As a result, adults over 50 are generally advised to get most of their B12 from fortified foods or supplements rather than relying solely on animal products.
People with digestive disorders (Crohn’s or celiac disease)
Conditions that have an effect on the digestive tract (like Crohn’s or celiac disease) can affect how well your body absorbs nutrients, including B12. If you have one of these conditions, your doctor might want to monitor your levels more closely.
Vegetarians or vegans
One of the main sources of vitamin B12 is animal products. We are talking about meat, fish, eggs, and dairy products. Most plant foods don’t naturally contain vitamin B12 unless they’ve been fortified. That’s why vegetarians and vegans have a higher risk of vitamin B12 deficiency.
Those taking certain medications
Some medications can lower B12 levels or make it harder to absorb. Acid-reducing drugs like omeprazole, lansoprazole, cimetidine, and ranitidine can affect vitamin B12 absorption. Other medications, like metformin, may also reduce B12 absorption and your blood levels over time.
So, if you are taking any of these medications, it’s important you talk to a doctor about whether you need to check your vitamin B12 levels.
People with pernicious anemia or autoimmune conditions
Pernicious anemia is an autoimmune condition that prevents the stomach from making intrinsic factor, the protein you need to absorb B12. Without it, even a diet rich in B12 won’t solve the problem, since it won’t get absorbed properly.
Additionally, people who’ve had stomach or intestinal surgery, including weight loss surgery, also face a higher risk, since these procedures can affect how well the body absorbs nutrients.
What are the symptoms of B12 deficiency?
B12 deficiency symptoms can be subtle at first and easy to mistake for everyday tiredness or stress. Here are some common signs you should be on the lookout for:
- Fatigue and weakness
- Cognitive issues (memory problems, confusion, and brain fog)
- Tingling or numbness (mainly in hands and feet)
- Mood changes (depression, anxiety, or irritability)
- Shortness of breath and dizziness
Other symptoms can include pale skin, heart palpitations, loss of appetite, unexplained weight loss, balance problems, and a sore mouth or tongue. Since these symptoms so easily overlap with other health conditions, it’s easy to overlook a B12 deficiency or mistake it for something else.
What foods are high in vitamin B12?
The best food sources of vitamin B12 are animal products: clams, beef liver, fish such as salmon, trout and tuna, beef, milk, yogurt, cheese and eggs. For plant-based eaters, fortified breakfast cereals, fortified plant milks and fortified nutritional yeast are the most reliable sources.
Check the nutrition label on fortified foods, since the amount of B12 added varies by brand. If you’re building a balanced plate, our everyday nutrition guide covers the basics, and if you’re eating less on a GLP-1 medication, see our guide to nutrition and GLP-1 medications.
How do you know if your B12 levels are low?
The most reliable way to confirm low B12 levels is through a blood test ordered by your healthcare provider. This test can measure the amount of vitamin B12 in your blood and can determine a deficiency even if your symptoms are mild or vague.
Sometimes, a doctor might recommend other tests like homocysteine or methylmalonic acid (MMA), since elevated levels can indicate a functional B12 deficiency even when blood levels appear to be normal.
If you’re experiencing any symptoms, or are in the at-risk groups, it’s important you speak with a doctor so you can both determine the best course of action.
How is B12 deficiency treated and prevented?
The treatment options are going to depend on the severity and cause of the deficiency. Here are some ways to help you manage and reduce the risk of vitamin B12 deficiency.
- Dietary changes: Increase your consumption of B12-rich foods like meat, fish, eggs, and dairy products. For plant-based options, consider fortified cereals, plant-based milk alternatives, and nutritional yeast.
- Oral supplements: Take over-the-counter B12 tablets or chewables for mild deficiencies. Always consult with your doctor before supplementing.
- B12 injections: For severe deficiencies or absorption issues, you can use regular B12 injections to help you restore your B12 levels.
- Lifestyle adjustments: Manage underlying health issues, such as digestive disorders that affect the absorption of vitamin B12.
- Routine testing: For people at risk, it’s important to get periodic blood tests to help you monitor B12 levels and detect any deficiencies early.
Taking metformin or an acid reducer? Ask your provider whether your B12 levels should be checked. Low B12 from these medications can build up slowly over years.
B12 injections vs. oral supplements: which works better?
Both can correct a deficiency. High-dose oral B12 works for many people, even with some absorption problems, while B12 injections bypass the digestive tract entirely. Injections are often preferred for severe deficiency, nerve symptoms, pernicious anemia, or after stomach or weight loss surgery.
A Cochrane review found that high-dose oral B12 and injections raised B12 levels similarly in many patients, so the right choice depends on the cause of your deficiency, how severe it is, and your preference. Injections also take the guesswork out of absorption, which is why many people with ongoing absorption issues choose them.
At DoctorAdam, a licensed provider can review your symptoms and history and, if appropriate, prescribe methylcobalamin B12 injections or our B12 Energy Boost Plus injection, shipped to your door. B12 is also part of our longevity and energy treatments.
Take your B12 levels seriously
B12 deficiency is very common and easy to overlook. No matter the cause, it’s important to understand your personal risk factors to catch a problem early.
If you’re experiencing symptoms like fatigue, tingling in your hands or feet, or unexplained mood changes, don’t try to diagnose yourself. Talk to your healthcare provider about testing and your treatment options.
Don’t wait to address your symptoms. Schedule a call with our doctors to determine if a vitamin B12 injection might be right for you!
Frequently asked questions
What are the first signs of low B12?
The first signs of low B12 are often tiredness, weakness, brain fog, pale skin, and tingling or numbness in the hands and feet. Because they come on slowly and look like everyday stress or aging, many people don’t connect them to B12 until a blood test shows low levels.
What causes vitamin B12 deficiency?
B12 deficiency is caused either by not getting enough B12 (for example, on a vegan or vegetarian diet) or by not absorbing it well. Poor absorption can come from low stomach acid with age, pernicious anemia, Crohn’s or celiac disease, stomach or weight loss surgery, and medications such as metformin and acid reducers.
Does metformin cause B12 deficiency?
Long-term metformin use is linked to lower B12 levels, and the risk grows with higher doses and longer use. If you take metformin, ask your provider about checking your B12 periodically, especially if you notice numbness, tingling or unusual fatigue.
Are B12 shots better than B12 pills?
Not always. High-dose oral B12 can raise levels in many people, even with some absorption problems. B12 injections bypass the gut, so they are often preferred for severe deficiency, nerve symptoms, pernicious anemia or after weight loss surgery. Your provider will recommend the right option based on your blood work and the cause of your deficiency.
How long do B12 injections take to work?
Many people notice more energy within a few days to a few weeks of starting B12 injections, and blood counts usually improve within weeks. Nerve-related symptoms such as tingling or numbness can take several months to improve, which is why early treatment matters.
Can low B12 cause anxiety, depression or mood changes?
Yes. B12 supports your brain and nervous system, so low levels are linked to irritability, low mood, anxiety and memory problems. Correcting a deficiency may help, but mood symptoms can have many causes, so talk to a provider rather than relying on B12 alone.
How much vitamin B12 do you need per day?
Most adults need 2.4 mcg of vitamin B12 per day. The recommendation rises to 2.6 mcg during pregnancy and 2.8 mcg while breastfeeding. Adults over 50 are advised to get much of their B12 from fortified foods or supplements because absorption from food declines with age.
Can you take too much vitamin B12?
Vitamin B12 has no established upper limit because your body excretes what it doesn’t need, and it is considered very safe at usual doses. Still, check with your provider before starting high-dose supplements or injections, especially if you have kidney disease or take other medications.
Can you get enough B12 from a plant-based diet?
It’s not so easy. B12 naturally occurs in animal products. So, strict vegans and vegetarians might need to rely on fortified foods and daily supplements.
Can you have normal B12 blood results and still be deficient?
Yes, standard B12 blood tests measure how much B12 is in your blood, but they don’t always reflect how well your body is actually using it. That’s why a doctor might recommend other tests like MMA.
How long does it take to recover from B12 deficiency?
Recovery time varies depending on the severity of the deficiency and the underlying cause. Mild cases may improve within a few weeks of starting supplements or making dietary changes. However, more severe deficiency might take several months of consistent treatment.
Sources
- Vitamin B12 deficiency – Nature Reviews Disease Primers (PubMed)
- Megaloblastic anemia – Cleveland Clinic
- Vitamin B12 status and absorption in older adults – PubMed Central
- Micronutrient deficiencies in Crohn’s disease – PubMed Central
- Vitamin B12 deficiency in celiac disease – PubMed
- Vitamin B12 in vegetarian and vegan diets – PubMed Central
- Vitamin B12 deficiency – Cleveland Clinic
- Vitamin B12 fact sheet for consumers – NIH Office of Dietary Supplements
- Oral versus intramuscular vitamin B12 for vitamin B12 deficiency – Cochrane Library
Brenda Peralta
Registered Dietitian Nutritionist (RDN) & Certified Diabetes Educator (CDE)
Brenda Peralta is a Registered Dietitian Nutritionist and Certified Diabetes Educator with experience translating nutrition and metabolic health science into practical, easy-to-understand guidance. Her work focuses on helping readers understand how nutrition, lifestyle, metabolic health, and healthy aging strategies can support long-term wellness and quality of life.
This article is for informational purposes only and does not replace medical advice. Prescription products require an online consultation with a licensed healthcare provider, who will determine whether treatment is appropriate for you.
