Vitamin B12 is an essential nutrient your body needs for processes such as DNA synthesis, energy production, and central nervous system function (1).
Although this vitamin is found in many foods, B12 deficiencies and deficiencies are relatively common. This is often associated with a restricted diet, malabsorption, certain medical conditions, or the use of medications that deplete B12 stores (2, 3, 4).
In fact, studies show that up to 20% of people over the age of 60 in the US and UK are deficient in this vitamin (5).
For reference, B12 levels above 300 pg/ml are considered normal, levels above 200-300 pg/ml are borderline, and levels below 200 pg/ml are considered deficient (2).
The ability to absorb B12 from food decreases with age, so deficiency is common in the elderly. However, this does not mean that children and young people, including pregnant and lactating mothers, cannot develop B12 deficiency (5, 6).
Unfortunately, B12 deficiency is often overlooked and misdiagnosed. Often this is due to insufficient laboratory tests or lack of symptoms of vitamin B12 deficiency (7).
If you suspect you have a B12 deficiency, it’s important to visit a healthcare professional to discuss your symptoms and get the proper testing.
This article discusses nine of the most common symptoms associated with B12 deficiency, as well as ways to diagnose and treat this deficiency.
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- Fatigue
If you are low or deficient in B12, you may experience fatigue.
Your body’s cells need B12 to function properly. Therefore, insufficient levels of B12 reduce the normal production of red blood cells and inhibit oxygenation (8).
In particular, deficiency of B12 or folic acid can cause megaloblastic anemia. This disorder causes large, abnormal, immature red blood cells and impaired DNA synthesis (2, 9).
If your body doesn’t have enough healthy red blood cells to carry oxygen to your tissues, you feel weak and tired.
Even if you think your B12 levels are borderline or limited, it’s important to know that fatigue and other symptoms associated with B12 deficiency can still occur (6).
- Pale or yellowish skin
Another symptom of B12 deficiency is pale or yellow skin.
Like a condition called iron-deficiency anemia, B12-deficiency anemia can cause the skin to turn pale because the body lacks fully matured healthy red blood cells (2).
B12 deficiency causes a condition called jaundice, which causes the skin and the whites of the eyes to turn yellow.
This color is caused by high levels of bilirubin, a byproduct of the breakdown of red blood cells in the body (2).
- Headache
B12 deficiency or deficiency can cause neurological side effects such as headaches.
In fact, headaches are one of the most common symptoms associated with B12 deficiency in both adults and children (2, 10, 11).
Some studies have shown that people with certain types of frequent headaches have low levels of B12.
A 2019 study of 140 people, half of whom had migraines, found that blood levels of B12 in migraineurs were significantly lower than in participants without migraines (12).
A study also found that people with the highest B12 levels were 80% less likely to develop migraines than those with the lowest B12 levels (12).
Research continues to investigate whether vitamin B12 treatment can improve migraine headache symptoms in some people (13).
- Symptoms of depression
B12 is essential for the normal functioning of the central nervous system, and a deficiency in this nutrient can affect your mental health.
In particular, B12 deficiency is associated with an increased risk of depression (14, 15).
Low levels of B12 can lead to elevated levels of a sulfur-containing amino acid called homocysteine. This, in turn, contributes to depression by increasing oxidative stress, DNA damage, and cell death in the body (16, 17).
A 2020 study of 132 children and adolescents, 89 with depression and 43 without depression, found that depressed participants had lower B12 levels and higher homocysteine levels than non-depressed children (17).
In addition to depressive symptoms, low or insufficient B12 levels can lead to other mental health disorders, such as psychosis and depression (18).
- Gastrointestinal problems
B12 deficiency can cause diarrhea, nausea, constipation,
bloating, gas and other gastrointestinal symptoms (2, 19).
These problems can occur in both adults and children (2, 20).
But remember that many of these symptoms are non-specific and can be caused by other factors. For example, food intolerances, medications, and infections can cause diarrhea.
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- Difficulties with concentration and mental disorders.
Because B12 deficiency affects the central nervous system, people with low or insufficient B12 levels may experience cloudiness, difficulty concentrating, and difficulty completing tasks ( 21Trusted Source ).
As the risk of B12 deficiency increases with age, older people are more likely to experience these side effects.
In general, many studies are related