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Vitamin B12
Deficiency
(Anemia)
What is vitamin B12–deficiency anemia?
Vitamin B12–deficiency anemia, also known as cobalamin
deficiency, is a condition that develops when your body
can't make enough healthy red blood cells because it doesn't
have enough vitamin B12. Your body needs vitamin B12 to make
healthy red blood cells, white
blood cells, and platelets.
Since your body doesn’t make vitamin B12, you have to get it
from the foods you eat or from supplements.
You can get vitamin B12 deficiency if you can’t absorb
vitamin B12 due to problems with your gut or if you have
pernicious anemia, which makes it difficult to absorb
vitamin B12 from your intestines. Without enough vitamin
B12, blood cells do not form properly inside your bone
marrow, the sponge-like tissue within your bones. These
blood cells die sooner than normal, leading to anemia.
What are the symptoms of vitamin B12–deficiency anemia?
If you have vitamin B12–deficiency anemia, you may have
the typical symptoms of anemia at first, such as
fatigue, paleness, shortness of breath, headaches, or
dizziness. If left untreated, you may start to notice
brain and nervous system symptoms. This is because
vitamin B12 is also needed for your brain and your
nerves to work properly.
Your symptoms may include:
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Tingling feelings or pain
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Trouble walking
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Uncontrollable muscle movements
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Confusion, slower thinking, forgetfulness, and
memory loss
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Mood or mental changes, such
as depression or irritability
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Problems with smell or taste
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Vision problems
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Diarrhea and weight loss
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Glossitis, which is a painful, smooth, red tongue
What causes vitamin B12–deficiency anemia?
You can develop vitamin B12–deficiency anemia if you do not
eat enough food with vitamin B12, such as if you follow a
strict vegetarian or vegan diet. But this is rare. In the
United States, vitamin B12–deficiency anemia is most often
due to other risk factors.
You can develop vitamin B12 deficiency for the following
reasons:
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Lack of intrinsic factor: Intrinsic factor is a
protein made in the stomach, which helps the body absorb
vitamin B12. People who have pernicious anemia do not
produce intrinsic factor. Pernicious anemia is more
common in people with northern European or African
ancestry. You may develop vitamin B12–deficiency anemia
if your body is not able to absorb enough vitamin B12
from the foods you eat. Older adults are more likely to
have digestive problems that make it harder to absorb
vitamin B12.
-
Lifestyle habits: Drinking too much alcohol can
make it harder for your body to absorb vitamin B12. For
men this is more than two drinks in a day. For women,
it’s more than one drink in a day.
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Medicines: Taking certain medicines can make it
harder for your body to absorb vitamin B12 over time.
These include some heartburn medicines and metformin to
treat diabetes.
-
Medical conditions: Some medical conditions can
raise your risk of vitamin B12–deficiency anemia.
These
include:
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Autoimmune diseases, such as celiac
disease, type 1 diabetes, and thyroid disease
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Chronic pancreatic disease
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Genetic conditions, such as Imerslund-Gräsbeck
syndrome, inherited intrinsic factor deficiency,
and inherited transcobalamin deficiency
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Intestinal and digestive conditions, such
as ulcerative colitis, Crohn’s disease, and
Helicobacter pylori infection
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Vitiligo
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Stomach surgery: Surgery on your stomach or
intestines, such as weight-loss surgery or gastrectomy,
can make it harder for your body to absorb vitamin B12.
How do you prevent vitamin B12 deficiency?
If you are otherwise healthy, maintaining a normal diet
enriched in vitamin B12 is important.
Foods that are good sources of vitamin B12 include:
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Lean red meat and chicken
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Fish, such as catfish and salmon; and seafood, such as
clams and oysters
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Milk, yogurt, cheese, and fortified vegan milk
substitutes
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Fortified cereals
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Eggs
How much vitamin B12 do you need each day?
The recommended daily amounts of vitamin B12 depend on your
age, your sex, and whether you are pregnant or
breastfeeding. Your healthcare provider can look at your
medical history to help determine how much vitamin B12 you
need each day.
Recommended Daily Amounts of Vitamin B12, in micrograms
(mcg)
Children and Adults |
Age |
Male or Female |
Pregnancy |
Breastfeeding |
1–3 years |
0.9 mcg |
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4–8 years |
1.2 mcg |
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9–13 years |
1.8 mcg |
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|
14–18 years |
2.4 mcg |
2.6 mcg |
2.8 mcg |
19–50 years |
2.4 mcg |
2.6 mcg |
2.8 mcg |
51+ years |
2.4 mcg (mostly from fortified foods or a supplement) |
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How is vitamin B12–deficiency anemia diagnosed?
To screen for vitamin B12–deficiency anemia, your healthcare
provider may order blood
tests to see whether you have low hemoglobin or
vitamin B12 levels.
Healthy and Abnormal
Blood Levels in Adults |
Hemoglobin, g/dL |
Normal |
Men: 13 or higher
Women: 12 or higher |
Anemia |
Men: 12 or lower
Women: 11 or lower |
Vitamin B12, pg/mL |
Normal |
400 or higher |
Vitamin B12-deficiency |
200 or lower (although levels may be normal in some
cases |
Tests to screen for vitamin B12-deficiency anemia.
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A
complete blood count measures hemoglobin.
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Another blood test
measures vitamin B12 levels in the blood.
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You may still have
the condition even if your vitamin B12 levels are normal.
How is vitamin B12–deficiency anemia treated?
If your doctor diagnoses you with vitamin B12–deficiency
anemia, your treatment will depend on the cause and
seriousness of your condition. Some people need lifelong
treatment.
Different therapies can be used to treat anemia.
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Vitamin B12 medicine can be prescribed by your provider for
you to take by mouth or as a nose spray or a shot. These
supplements can help increase the levels of vitamin B12
in your body. For serious vitamin B12–deficiency anemia,
your doctor may recommend vitamin B12 shots until your
levels are healthy.
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Blood transfusions to treat serious vitamin
B12–deficiency anemia in combination with vitamin B12
treatment.
Your care provider may also recommend you make some changes
to your eating habits to help increase the amount of vitamin
B12 in your diet.
Some symptoms may take months to improve, depending on how
serious they are. Some symptoms related to the brain or the
nerves, such as numbness and tingling, may not go away even
with treatment.
What happens if vitamin B12–deficiency anemia is not treated?
Vitamin B12–deficiency may cause serious complications,
such as bleeding, infections, and problems with your
brain or nerves that may be permanent. Babies born to
mothers who have vitamin B12–deficiency may have
developmental delays and birth defects of the brain and
spinal cord.
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