There are so many different types of vitamins out there, and they all work in tandem to nourish your body. Often, you can get all the vitamins you need from a healthy diet and multivitamins. But sometimes—despite your best efforts—you'll end up deficient in something, be it a mineral, like magnesium, or an important vitamin, like B12
"Vitamin B12 is a water-soluble vitamin that is found primarily in foods from animal products, including meat, eggs, dairy, and shellfish," says Andrew Cunningham, MD, a family practitioner and integrative physician. "Since human cells cannot produce it, we rely on our diet to provide it."
Although daily B12 requirements are fairly low—just 2.4 micrograms for teenagers and adults—it plays a crucial role in metabolic and cellular processes. Says Omayra Quijano-Vega, MD, an endocrinologist and thyroid specialist, "B12 is the catalyst for red blood cell production, DNA synthesis, protein conversion, neurological function, fatty acid synthesis, and nerve health."
Population studies suggest as much as 40% of the population has a vitamin B deficiency, says Taylor Graber, MD, an anesthesiologist and founder of ASAP IVs. Vegetarians and vegans are most at risk since they don't get an adequate amount of B12 in their diet without supplementation. Other chronic health conditions, like Crohn's disease or hypothyroidism, can also up your risk factor since your body can't readily absorb nutrients. Of course, you can also end up with a vitamin B12 deficiency even if you don't fall into either of these camps.
Symptoms of a Vitamin B12 Deficiency
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Symptoms tend to develop slowly and may not be recognized immediately, says Quijano-Vega. As the condition worsens, she says common symptoms include the following:
Weakness and fatigue: Vitamin B12 helps make red blood cells, which are the carriers of oxygen throughout the body. If you don't have enough, you can feel tired and weak.
Light-headedness or dizziness: If you have a B12 deficiency so significant that it causes anemia, you will feel light-headed and dizzy on exertion. This is because you don't have enough oxygen throughout your body.
Heart palpitations and rapid heartbeat: Heart palpitations are one symptom of anemia, and if your anemia is caused by low B12, it can lead to heart palpitations.
Shortness of breath: Similarly, if you have anemia from a low amount of vitamin B12 and a lower amount of red blood cells circulating, you can experience difficulty with a full inhale.
A sore tongue that has a red, beefy appearance: A low vitamin B12 decreases iron. Because iron controls levels of myoglobin, a substance in the blood that is very important in the role of all muscle health, including the tongue, you may notice an impact on the tongue. This is most common for those on a vegetarian diet.
Nausea or poor appetite: When you are weak and your body doesn't get enough oxygen, it can cause a decreased appetite and nausea.
Weight loss: Not surprisingly, when you are nauseous and have a poor appetite and other gastric symptoms associated with B12 deficiency, it can result in weight loss.
Diarrhea: Vitamin B12 can affect the digestive tract. When there aren't enough red blood cells, it means that not enough oxygen reaches the gut. This can lead to feeling sick, causing diarrhea.
Constipation: Due to the gut issues associated with a vitamin B12 deficiency, one can get constipation as the gut reacts to the deficiency.
What Happens If Your Deficiency Is Left Untreated
If low levels of B12 remain for a long time, the condition can lead to irreversible damage to nerve cells, says Quijano-Vega. If this happens, you may notice the following symptoms:
Numbness and tingling in the hands and feet: Vitamin B12 plays an important role in the nervous system function. When it’s low, it can cause nerve conduction issues or even nerve damage, which can lead to numbness and tingling.
Difficulty walking: Because of the nerve issues and neurologic effects, a vitamin B12 deficiency can lead to movement issues that can make it hard to walk without support.
Muscle weakness: Since vitamin B12 is important to muscle and nerve function, one can experience the feeling of muscle weakness with a low vitamin B12.
Irritability: Vitamin B12 helps break down a chemical in the brain called homocysteine, and having too much of homocysteine in the brain can lead to mental health problems such as irritability and, in more severe cases, dementia or psychosis.
Memory loss: Vitamin B12 and other B vitamins are important in the production of brain chemicals that affect mood and other brain functions.
The number one way to confirm a vitamin B12 deficiency is through a blood test, says Niket Sonpal, MD, an internist and gastroenterologist in New York City. If you have a vitamin B12 deficiency, this test may reveal low levels of a substance called methylmalonic acid, abnormal and low white blood cells, and the presence of antibodies that indicate anemia, says Sonpal.
The good news: Vitamin B12 deficiency is treatable if you notice the signs and get help from a doctor early, says Sonpal. The severity of your deficiency will determine treatment. Vitamin B12 deficiency resulting from inadequate dietary intake is the easiest to treat, says Quijano-Vega. The condition can be reversed by taking 1000 micrograms of oral vitamin B12 supplements per day and adding foods containing B12. In more severe cases, your physician may recommend intravenous or intramuscular injections, says Graber.
Editor-Recommended Vitamin B12 Supplements
Considering taking a supplement? Take a look at some of our editor favorites below. But remember: It's best to chat with your doctor before you start consuming any of these or other vitamins.