Are you experiencing unexpected fatigue, tingling fingers or hair loss? While this could be the result of a variety of health conditions, it could also signal a vitamin deficiency.

In the United States, severe vitamin deficiencies and malnutrition are rare. However, many people present with some level of micronutrient inadequacy, which means they are not meeting the estimated average requirement for certain vitamins. According to data from the 2005-2016 National Health and Nutrition Examination Surveys, the following presented with micronutrient inadequacies among the U.S. population:

Vitamin deficiencies can result from genetics, co-occurring health conditions or a diet that lacks essential micronutrients. When they occur, they can harm the body and increase risks for health complications.

There are two categories of vitamins: water-soluble and fat-soluble vitamins, both of which impact how they are stored in the body and could influence the likelihood of you becoming deficient in a certain vitamin. Water-soluble vitamins dissolve in water and are filtered out by the kidneys. Because they are removed from the body quickly, they need to be replenished regularly. On the other hand, fat-soluble vitamins dissolve in fat and are stored for a longer period of time in the body’s tissue, which can potentially lead to toxicity if you over-supplement.

Depending on the level of deficiency, you may be able to simply add more food-based sources or you may need to supplement with a vitamin.

Vitamin B12 Deficiency

David Cutler, a family medicine practitioner at Saint John’s Physicians Partners in Santa Monica, California, says that of the vitamin deficiencies he sees, vitamin B12 deficiencies are the most common.

Vitamin B12 is a water-soluble vitamin that plays a vital role in central nervous system functioning, healthy red blood cell formation and DNA synthesis. Experts say that levels of less than 150 picograms per milliliter of vitamin B12 may warrant a deficiency, which can be measured through blood serum and plasma tests.

Because vitamin B12 is only naturally found in animal products, people who follow a strict vegetarian or vegan diet can be at risk for vitamin B12 deficiencies. However, as long as people take a vitamin B12 supplement, which is widely available, they can avoid falling short on this micronutrient.

Pernicious anemia

Some people have vitamin B12 deficiencies as a result of pernicious anemia, a rare condition in which the body is unable to absorb vitamin B12, leading to a reduction in red blood cell production. If untreated, pernicious anemia can cause lasting nerve damage.

Pernicious anemia can often be treated with intravenous injections of vitamin B12. Among those diagnosed with pernicious anemia, it is most common in older adults ages 60 and up.

Symptoms

Vitamin B12 deficiencies can cause a range of health complications that can impact physical and mental health. Some symptoms include:

Vitamin B12 deficiencies may also increase risks for neurological conditions, like dementia, and mental health conditions, like depression.

How to treat

Not surprisingly, the antidote for a vitamin B12 deficiency is vitamin B12. People can get vitamin B12 through food, including:

For a non-dietary approach, vitamin B12 can be taken as an oral supplement, sublingual tablet, nasal spray or intravenous injection. Injections are most helpful for people who cannot absorb vitamin B12 from food or supplements.

If you have a vitamin B12 deficiency and are worried about malabsorption, it’s a good idea to work with your health care provider. Your doctor may recommend you start taking oral vitamin B12 supplements, then check your blood levels again in a few weeks to assess whether the supplement is working and determine an alternative course of action.

Vitamin A Deficiency

Vitamin A is a fat-soluble vitamin that supports white blood cell formation, cell growth, bone health and eye health.

Vitamin A deficiencies are rare in the U.S.

“It probably exists, but it’s extremely rare,” Cutler says. “Anybody who eats any amount of fruits, vegetables and meat products is going to have adequate vitamin A.”

Symptoms

When vitamin A deficiencies do occur, people may experience new skin or vision issues, says Cesar Sauza, a registered dietitian and clinical nutrition manager with AltaMed Health Services.

On the other hand, vitamin A toxicity – in which the body has too much vitamin A – may be more common than a deficiency. One reason for this is because vitamin A is fat soluble – meaning it dissolves in fat and is stored in the body’s tissue – and, therefore, not excreted as quickly as water-soluble vitamins. People often get adequate amounts of vitamin A through their diet, so taking vitamin A supplement is often not recommended.

Some symptoms of vitamin A toxicity may include:

How to treat

Many healthy foods contain vitamin A, so it can be smart to include them in your diet rather than supplementing with a vitamin A pill.

High-vitamin A foods include:

Vitamin B Deficiencies

As you may have guessed from vitamin B12’s listing above, there are multiple B vitamins. The group supports a range of functions in the body, like breaking down food and transporting oxygen to cells. Other than B12, two common B vitamins you may have heard of are vitamin B9, also known as folate, and vitamin B7, also known as biotin. B vitamins are all water soluble.

The eight B vitamins are:

Symptoms

Deficiency in any of the B vitamins may cause symptoms, such as:

Pregnant people and those who are breastfeeding require more vitamin B9 (folate). A deficiency can increase risks for the child to be born with birth defects, like spina bifida and anencephaly. In addition, because dialysis removes folate, people with kidney disease are at risk for a folate deficiency and require supplementation.

Vitamin B7 (biotin) deficiencies may cause symptoms like hair loss, skin problems and brittle nails.

How to treat

These deficiencies can often be prevented with a healthy diet that includes fruits and vegetables, Cutler says.

To address or prevent a vitamin B deficiency, try incorporating foods that contain high levels of vitamin B into your diet, such as whole grains, tuna, spinach and liver, Sauza says.

Some foods that contain biotin include:

Some foods that contain folate include:

If you want more than food alone, you can purchase vitamin supplements. Folate can be taken as folic acid, which researchers say can be better absorbed than folate in food. Biotin supplements are also available for purchase and are incredibly popular. From 1999 to 2016, the number of people using biotin supplements increased by nearly 30 times, according to research funded by the National Heart, Lung and Blood Institute.

Despite high numbers of use, research is lacking on the effectiveness of biotin supplementation. Studies are inconclusive about whether biotin supplementation can remedy hair, skin and nail problems or support hair growth for people who are not biotin deficient.

Vitamin C Deficiencies

Vitamin C is a water-soluble vitamin that plays a role in fighting infections, wound healing and producing collagen proteins.

Vitamin C deficiencies are rare in developed countries like the U.S., “but are most commonly seen in individuals living with food insecurity,” Sauza says. This can be due to people not having enough healthy fruits and vegetables in their diet.

Symptoms

People who are deficient in vitamin C may experience symptoms like:

Serious cases of vitamin C deficiencies can lead to scurvy, a disease caused by loss of collagen.

How to treat

While vitamin C supplements are available, you can incorporate more citrus fruits into your diet first.

Foods that contain vitamin C include:

Vitamin D Deficiency

Vitamin D is a fat-soluble vitamin that aids in calcium and phosphorus absorption in the body, supporting bone health. Not only is it one of the most common nutrient deficiencies in the U.S., it is also one of the most serious deficiencies doctors encounter.

Vitamin D is “involved in so much in our body, it acts as a hormone rather than a vitamin,” Sauza says.

Vitamin D plays a vital role in the body by aiding in the absorption of calcium and phosphorus, which are essential for maintaining healthy bones and teeth. A deficiency in vitamin D can lead to weakened bones and impact immune function, cardiovascular health and brain health.

“The reasons for vitamin D deficiency could be related to sun exposure, although it is also common to see vitamin D deficiency in those with plenty of sun exposure,” Sauza says.

Vitamin D deficiency is even higher in individuals with darker skin pigmentation and among patients who are severely overweight or obese, but it is unclear why this correlation exists, he adds.

Symptoms

Symptoms of a vitamin D deficiency include:

In some cases, prolonged vitamin D deficiency in children can cause rickets, a condition defined by soft or poorly developed bones.

How to treat

To increase vitamin D in your diet, opt for foods like:

Vitamin E Deficiency

Vitamin E is a fat-soluble vitamin that acts as an antioxidant and helps protect cells.

Vitamin E deficiencies are rare and typically do not cause symptoms, Sauza says. Most people don’t consume a lot of vitamin E as it is, and the good news is that most of us aren’t paying for it.

Symptoms

Symptoms of a vitamin E deficiency include:

Vitamin C or vitamin D deficiencies may also lead to a weakened immune system, so Sauza says not to self-diagnose yourself with a vitamin E deficiency next time you are sick.

How to treat

Many healthy foods contain vitamin E, so including them into your diet will help nourish you regardless of a potential deficiency.

Some foods high in vitamin E include:

Vitamin K Deficiency

Vitamin K is a fat-soluble vitamin that helps make proteins needed for blood clotting and bone-building.

Vitamin K problems are rare but can be severe, Sauza says. They can lead to complications like bleeding without blood clots. Because vitamin K is fat-soluble, people may be at higher risk for vitamin K toxicity than deficiency.

“When discussing vitamin K, the concern is usually on medication-nutrient interactions as eating high amounts of vitamin K can interact with common anticoagulants,” Sauza says.

Symptoms

Vitamin K deficiencies are uncommon. When they do occur, symptoms may include:

How to treat

Since most people are not vitamin K deficient, you probably don’t need to worry about your vitamin intake or take a vitamin K supplement. Still, here are some foods that are good sources of vitamin K:

Bottom Line

While vitamin deficiencies can be serious, they can be largely prevented by eating a healthy, well-balanced diet full of fruits, vegetables, whole grains and lean animal products.

If you are otherwise nervous about vitamin deficiencies, talk to your doctor about getting a blood test to check your levels.