Blood test

Low vitamin B12 level in the blood

Blood test
Low vitamin B12 level in the blood
Last update: 03/05/2022

What is low vitamin B12 level in the blood called?

  • Hypocobalaminemia

What is the normal level of vitamin B12 in the blood?

If you need to know which are the vitamin B12 reference ranges or you require more information about vitamin B12 in a blood test, you can visit normal vitamin B12 in a blood test.

What does a low vitamin B12 level in the blood mean?

Vitamin B12, also known as cobalamin, is essential for the correct production of Red Blood Cells (RBCs). Deficiency of vitamin B12 may cause anemia.

Deficiency of vitamin B12 is related to megaloblastic anemia (a type of anemia) and neuropathy (damage to nerve cells).

The most common cause for a low value of vitamin B12 in the blood is pernicious anemia. However, there are many other causes for a low value of vitamin B12 in the blood. They can be classified as:

  • Vitamin B12 deficiency
    • Pernicious anemia (due to lack of intrinsic factor)
    • Dietary deficiency (it is rare but may be seen in case of strict vegetarian diets)
  • Malabsorption of vitamin B12
    • Aclorhydria
    • Diseases of the ileum
    • Regional enteritis
    • Genetic disorders such as Imerslund-Gränsbeck syndrome
    • Gastric surgery (gastric bypass surgery, gastrectomy or ileal resection)
  • Intestinal causes
    • Intestinal parasites such as fish tapeworm infestation of the genus Diphyllobothrium (Diphyllobothriasis)
    • Tropical sprue
  • Medication to neutralize stomach acidity (antacids)
    • H2 receptor antagonists (ranitidine)
    • Proton pump inhibitor drugs (omeprazole, esomeprazole, etc.)

Vitamin B12 blood values are usually given in pg/dl but sometimes you can see these values in pmol/l following the International System of Units (SI). In case your values are in pmol/l you can convert them using this tool:


Hypocobalinemia or a low vitamin B12 blood level means:

  • Mild hypocobalaminemia (100 - 200 pg/ml in adults):

    Vitamin b12 level in the blood is below the normal range. It is necessary to pay attention because usually there are no symptoms related.

    It may be due multiple causes such as some drugs or deficient intake on vegetarian people.

    If the level remains low in successive tests, you should ask your doctor about it.

  • Severe hypocobalaminemia (< 100 pg/ml in adults):

    Values of vitamin B12 below 100 pg/ml are common in case of suffering from pernicious anemia. Pernicious anemia is a macrocytic anemia where the MCV are above 100 fl. You may feel fatigue, headache or paleness as a consequence of the anemia.

    There are other possible causes for a low level of vitamin B12 in the blood, so it is advisable to visit your doctor. He may prescribe you intramuscular injections of vitamin B12.

Which factors can reduce the vitamin B12 level in the blood?

Some particular health situation or drugs may reduce your vitamin B12 level in the blood:

  • Gastric surgery
  • Vegetarian diet
  • Pregnancy
  • Nitrous acid exposure
  • Malnutrition
  • Drugs
    • Antacids
      • Esomeprazole
      • Lansoprazole
      • Omeprazole
    • Antibiotics
      • Neomycin
    • Anti-diabetic medication
      • Metformin
    • Antihypertensives
      • Sodium nitroprusside
    • Drugs for acid related disorders
      • Ranitidine
    • Colchicine

Which diseases can reduce your vitamin B12 level in the blood?

The following diseases can explain a vitamin b12 blood level lower than normal:

  • Sprue
  • Giardiasis
  • Chronic pancreatitis
  • Pancreatic insufficiency
  • Zollinger–Ellison syndrome
  • Achlorhydria
  • Autoimmune atrophic gastritis

What can I do to increase the vitamin B12 level in the blood?

Vegetarians may have a vitamin B12 deficiency because meat is the main source of this type of vitamin. In this case, you may take vitamin B12 supplements, if your doctor considers it appropriate.

Depending on the underlying cause and if the deficiency is related to malabsorption, your doctor may prescribe intramuscular injections of vitamin B12.

Where can I find more information about vitamin B12 level in the blood?

You can visit our pages about:

Which values are considered a low vitamin B12 level in the blood?

The following values are considered to be above the normal range:

IMPORTANT: These levels are expressed in pg/ml. They are an example of a healthy adult of about 45 years old with no known disease and not taking any medication. The ranges can be different depending on the laboratory or on your personal circumstances.

Vitamin B12
Mild hypocobalaminemia
199 pg/ml198 pg/ml197 pg/ml196 pg/ml195 pg/ml194 pg/ml193 pg/ml192 pg/ml
191 pg/ml190 pg/ml189 pg/ml188 pg/ml187 pg/ml186 pg/ml185 pg/ml184 pg/ml
183 pg/ml182 pg/ml181 pg/ml180 pg/ml179 pg/ml178 pg/ml177 pg/ml176 pg/ml
175 pg/ml174 pg/ml173 pg/ml172 pg/ml171 pg/ml170 pg/ml169 pg/ml168 pg/ml
167 pg/ml166 pg/ml165 pg/ml164 pg/ml163 pg/ml162 pg/ml161 pg/ml160 pg/ml
159 pg/ml158 pg/ml157 pg/ml156 pg/ml155 pg/ml154 pg/ml153 pg/ml152 pg/ml
151 pg/ml150 pg/ml149 pg/ml148 pg/ml147 pg/ml146 pg/ml145 pg/ml144 pg/ml
143 pg/ml142 pg/ml141 pg/ml140 pg/ml139 pg/ml138 pg/ml137 pg/ml136 pg/ml
135 pg/ml134 pg/ml133 pg/ml132 pg/ml131 pg/ml130 pg/ml129 pg/ml128 pg/ml
127 pg/ml126 pg/ml125 pg/ml124 pg/ml123 pg/ml122 pg/ml121 pg/ml120 pg/ml
119 pg/ml118 pg/ml117 pg/ml116 pg/ml115 pg/ml114 pg/ml113 pg/ml112 pg/ml
111 pg/ml110 pg/ml109 pg/ml108 pg/ml107 pg/ml106 pg/ml105 pg/ml104 pg/ml
103 pg/ml102 pg/ml101 pg/ml100 pg/ml    
Severe hypocobalaminemia
99 pg/ml98 pg/ml97 pg/ml96 pg/ml95 pg/ml94 pg/ml93 pg/ml92 pg/ml
91 pg/ml90 pg/ml89 pg/ml88 pg/ml87 pg/ml86 pg/ml85 pg/ml84 pg/ml
83 pg/ml82 pg/ml81 pg/ml80 pg/ml79 pg/ml78 pg/ml77 pg/ml76 pg/ml
75 pg/ml74 pg/ml73 pg/ml72 pg/ml71 pg/ml70 pg/ml69 pg/ml68 pg/ml
67 pg/ml66 pg/ml65 pg/ml64 pg/ml63 pg/ml62 pg/ml61 pg/ml60 pg/ml
59 pg/ml58 pg/ml57 pg/ml56 pg/ml55 pg/ml54 pg/ml53 pg/ml52 pg/ml
51 pg/ml50 pg/ml49 pg/ml48 pg/ml47 pg/ml46 pg/ml45 pg/ml44 pg/ml
43 pg/ml42 pg/ml41 pg/ml40 pg/ml39 pg/ml38 pg/ml37 pg/ml36 pg/ml
35 pg/ml34 pg/ml33 pg/ml32 pg/ml31 pg/ml30 pg/ml29 pg/ml28 pg/ml
27 pg/ml26 pg/ml25 pg/ml24 pg/ml23 pg/ml22 pg/ml21 pg/ml20 pg/ml
19 pg/ml18 pg/ml17 pg/ml16 pg/ml15 pg/ml14 pg/ml13 pg/ml12 pg/ml
11 pg/ml10 pg/ml9 pg/ml8 pg/ml7 pg/ml6 pg/ml5 pg/ml4 pg/ml
3 pg/ml2 pg/ml1 pg/ml0 pg/ml    
Medically reviewed by our Medical staff on 03/05/2022


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