- Vitamin B12 deficiency develops slowly but can cause lasting damage if untreated.
- Warning signs include fatigue, tingling hands or feet, a red tongue and memory issues.
- Boost your intake with vitamin B12-rich foods and consult your healthcare provider about supplementation.
Vitamin B12 may not be the first nutrient that comes to mind when you think about health, but your body depends on it for essential functions. It helps maintain proper nerve function, supports the production of healthy red blood cells and is crucial for DNA synthesis.
When B12 levels fall too low, these critical processes can become impaired. Symptoms of deficiency often develop gradually, sometimes over months or even years, making them easy to overlook. If left untreated, they can worsen and potentially lead to long-term damage.
That’s why early detection is so important. We asked dietitians to share six sneaky signs of vitamin B12 deficiency so you can catch them before they escalate.
1. Feeling Very Tired and Weak
If you’ve been feeling unusually fatigued, those persistent waves of tiredness or weakness could be an early sign of low vitamin B12. “When you’re low on B12, your body can’t make enough healthy red blood cells to carry oxygen efficiently. That means your tissues and organs aren’t getting the oxygen they need, leaving you feeling wiped out even after a full night’s sleep,” says Whitney English Tabaie, M.S., RDN, CPT.
She notes that many people describe this feeling as a deep, dragging tiredness, like running on low battery power all day. As a result, low vitamin B12 levels can make everyday tasks feel heavier and more difficult than usual.
2. Pale or Yellow Skin
Another subtle sign of vitamin B12 deficiency is a change in skin color. When B12 levels drop, the resulting shortage of red blood cells can cause the skin to appear pale and dull, explains English Tabaie. In some cases, your skin or the whites of your eyes can even turn slightly yellowish, which is a sign of mild jaundice. “This happens because without enough B12, red blood cells become fragile and break down easily, releasing a pigment called bilirubin that can give the skin a yellow tint,” she explains.
3. Numbness in Hands or Feet
While it’s easy to dismiss numbness or tingling in the hands and feet as a result of sitting too long or poor circulation, it can actually indicate vitamin B12 deficiency. “Vitamin B12 is essential for maintaining the protective sheath (myelin) that surrounds nerves. Without enough of it, nerve signals can misfire, causing that characteristic tingling, burning or numb sensation, usually in the extremities first,” says English Tabaie. If left untreated, she warns, this can progress to balance issues, difficulty walking and even permanent nerve damage.
4. Dizziness and Rapid Breathing
Moments when the room feels like it’s spinning and your breathing picks up can be subtle signs of low vitamin B12. English Tabaie explains that this happens when the blood isn’t carrying enough oxygen to the heart and lungs. As a result, these organs go into overdrive to compensate for lower oxygen levels by speeding up your breathing and heart rate. “That can leave you light-headed or dizzy, especially when standing up quickly or exerting yourself,” she adds. While it’s easy to mistake these symptoms for dehydration or stress, they may actually signal that you need to increase your vitamin B12 intake.
5. Memory or Mood Changes
If your memory starts slipping or your mood shifts more easily than usual, it may be a sign that your vitamin B12 is in short supply. “B12 helps make neurotransmitters that influence mood and cognition, so low levels can affect mental sharpness and emotional health,” says English Tabaie.
When brain cells don’t receive the nutrients they need, you may feel forgetful, foggy, anxious or even depressed. In more severe cases, confusion or dementia-like symptoms can develop, making early detection and treatment especially important.
6. Sore Red Tongue
A lesser-known symptom of vitamin B12 deficiency is a sore, red or “beefy” tongue. English Tabaie explains that vitamin B12 plays a key role in regulating the rapidly dividing cells that line the mouth and tongue. “A lack of [vitamin B12] can cause the papillae (the little bumps that contain taste buds) to disappear, leading to pain, smoothness and altered taste sensations,” she explains. You might also notice your tongue developing a glossy or shiny appearance. If you spot any of these changes, it could be a clue that your body is running low on this crucial nutrient.
How to Boost Your Vitamin B12 Intake
If your symptoms and recent bloodwork suggest low vitamin B12, the good news is that there are effective ways to restore your levels. For most adults, the recommended daily intake is 2.4 micrograms, with slightly higher needs during pregnancy (2.6 mcg) and lactation (2.8 mcg), notes English Tabaie.
Since vitamin B12 is naturally found in animal products, you can meet these requirements by eating lean meats, fish and seafood, dairy and egg yolks. For vegetarians and vegans, getting the recommended amount of vitamin B12 from natural sources can be harder. Fortunately, fortified foods, such as plant-based milks, nutritional yeast, meat substitutes and breakfast cereals, can help bridge the gap.
However, “B12 also needs something called intrinsic factor to help with absorption,” says Alexandra Caspera, M.A., RD. As we age, our bodies produce less stomach acid, making it harder to release vitamin B12 from food and bind it to intrinsic factor. For this reason, vitamin B12 deficiency becomes more common with age. It can also occur in people with pernicious anemia, an autoimmune condition in which the body attacks stomach cells responsible for producing intrinsic factor. In these cases, supplementation can be especially helpful.
“Vitamin B12 supplements are more effective than food as they don’t require stomach acid and other enzymes for absorption,” explains Caspera. She recommends supplements for adults over 50, individuals taking proton pump inhibitors or other acid-reducing medications, those on metformin, and anyone on a primarily plant-based diet. However, you should consult your healthcare provider to ensure it’s right for you.
“Because of the unique way that B12 is absorbed, you’ll need a much higher dose of B12 if taken in a single dose,” she emphasizes. Both dietitians note that a daily dose of 25 to 100 mcg may be necessary to maintain adequate levels, since only about 1 to 2% is absorbed at a time.1 For severe deficiency, doses of 500 to 1,000 mcg may be required under medical supervision.
When to See a Healthcare Professional
If you are experiencing persistent fatigue, numbness in your hands or feet, memory changes, balance issues or other sudden changes in your health, seek medical attention as soon as possible. Early diagnosis and treatment by a healthcare provider are key to preventing long-term complications and restoring healthy vitamin B12 levels.
Our Expert Take
Fatigue, numbness, pale or yellow skin, dizziness, mood changes and a red or swollen tongue can be subtle but important warning signs of vitamin B12 deficiency. Recognizing these signs early can help prevent lasting damage. If you have any concerns, consult a healthcare professional who can assess your vitamin B12 status and guide you toward the right solution, whether that’s increasing vitamin B12-rich foods, choosing fortified options or adding a supplement to restore healthy levels. By tuning into your body’s signals and taking action early, you can stay sharp, energized and in control of your health.
