9 signs you have a vitamin B12 deficiency, and why you need to boost your levels

• Recent research has studied the link between vitamin B12 deficiency and cognitive decline in older people.
• Though more research is needed on vitamin B12 and neurological behavior, the nutrient is essential for producing energy.

Vitamin B12 is an easy vitamin to get, whether through foods or supplements — which is a good thing because deficiency can cause long-lasting damage to your nerves and cognition.

Recent research has found higher rates of cognitive decline in older people who have both a vitamin B12 deficiency and an excess with either folic acid or vitamin B9, said Dr. Eduardo Villamor, a professor of epidemiology at the University of Michigan.

Some research has suggested vitamin B12 can help with depression and prevent dementia, but Villamor said more research is needed on the impact vitamin B12 has on neurological behavior.

"There is substantial interest on the role of vitamin B-12 on neurocognitive performance, especially in the elderly," Villamor said. "The role of vitamin B-12 on fetal, infant, and child neurodevelopment is also an important area of research."

Here's how to know if you're deficient in vitamin B12 and why you need the important nutrient:

Symptoms of vitamin B12 deficiency range from mild fatigue to severe neurological complications

Villamor said people lacking in vitamin B12 develop a range of symptoms depending on how long they are deficient in the nutrient.

People with a mild vitamin B12 deficiency could develop fatigue, he said. Vitamin B12 reacts with compounds in the body to produce DNA and energy, which is why a deficiency can lead to tiredness.

Mild to moderate vitamin B12 deficiency may cause anemia, or when the body lacks enough healthy red blood cells to help distribute oxygen. Dr. Aaron Goodman, a hematologist and professor at UC San Diego Health, previously told Insider that anemia caused by vitamin B12 deficiency produces cracks or sores around the mouth.

Villamor said moderate vitamin B12 deficiency could lead to a form of anemia called macrocytosis, or when red blood cells enlarge. The condition does not typically produce symptoms, according to Mayo Clinic, but can show up on routine blood tests.

Moderate deficiency may also lead to peripheral neuropathy, or damage to the nerves outside the brain and spinal cord. Symptoms of peripheral neuropathy include sensory problems like tingling or numbness in the hands and feet, and glossitis, or tongue inflammation that might result in sensitivity to spicy or acidic food.

Severe deficiency could result in "serious neurological and psychiatric manifestations," Villamor said. Neurological symptoms include:

• Irritability
• Impaired cognition
• Depression
• Psychosis
• Dementia

Some neurological symptoms can become permanent if the vitamin B12 deficiency goes untreated, registered dietitian Elizabeth Beil previously told Insider.

Severe vitamin B12 deficiency may also cause more serious anemia and problems with other blood cells, inflammation and weakening of the heart, and even infertility, per Villamor.

Treating vitamin B12 deficiency

Villamor said people at highest risk of B12 deficiency are those with low intake of animal foods like eggs and meat, which are the only natural source of the vitamin. These people might not eat enough animal foods "either by choice, for example strict vegetarians, or due to socioeconomic constraints, as in many low and middle income countries where animal foods can be expensive," Villamor said.

Vitamin B12 deficiency can be prevented through the intake of animal foods "if choice and purchasing power allow," Villamor said, or through oral supplements and fortified foods. Other treatments include intramuscular shots or an IV drip.

The doctor added older adults or people who have undergone stomach surgery like a bypass might have a type of malabsorption that can cause vitamin B12 deficiency. People taking medication to decrease stomach acid and alcohol drinkers may also be at risk, Villamor said.