To screen for and detect moderate to severe vitamin B deficiencies
B Vitamins
When you have symptoms that may be due to a B vitamin deficiency, are at risk for a deficiency, or have a condition associated with malabsorption
A blood sample drawn from a vein in your arm; a random or 24-hour urine sample may also be collected.
Fasting is usually required for blood testing.
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How is it used?
One or more B vitamin tests may be used to screen for and detect deficiencies in people with characteristic symptoms.
Testing may also be used for those who have a condition that puts them at risk of B vitamin deficiencies. This may include individuals with a limited or inadequate diet, those with signs of malnutrition, those being given their nutrition intravenously (parenteral nutrition), and those who have had gastric bypass surgery. Testing may also be performed for those with alcoholism or with chronic diseases associated with malabsorption, such as Celiac disease.
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When is it ordered?
Testing is primarily ordered when a person has symptoms that may be due to a B vitamin deficiency. Signs and symptoms depend on the vitamins that are deficient. Some of the common ones include:
- Rash, dermatitis
- Inflamed tongue, sores on the lips or in the mouth, cracks at the corners of the mouth
- Numbness, tingling or burning in the hands or feet (peripheral neuropathy)
- Anemia
- Fatigue, insomnia
- Irritability, difficulty with memory, depression
B vitamin testing may be used when a person has a condition that puts them at risk for a deficiency. Those at increased risk include people who are malnourished, are chronic alcoholics, or who have a condition such as Celiac disease that is associated with malabsorption.
B vitamin toxicity rarely occurs so testing for this purpose is not often done. High concentrations of a few of the B vitamins may affect the liver or nervous system.
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What does the test result mean?
Test results that are low may indicate a B vitamin deficiency but will not reveal whether it is due to an inadequate supply or an inability to absorb or use available B vitamins. When someone is deficient, the person often has multiple vitamin deficiencies.
If test results are normal, then it is more likely that a person's symptoms are due to another cause.
A high B vitamin level may be associated with vitamin toxicity. This rarely occurs and when it does, it is usually due to exposure to high doses of the vitamin.
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Is there anything else I should know?
A person may sometimes be diagnosed and treated for a B vitamin deficiency based upon clinical findings and a response to treatment, rather than testing. For instance, if a healthcare provider suspects a B1 deficiency, the provider may prescribe B vitamin supplements and then monitor the person to see if symptoms resolve.
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What are the Recommended Dietary Allowances (RDA) for B vitamins?
The RDA for adults, children, and other groups vary by the specific B vitamin. To determine the RDA for a particular vitamin, see the Dietary Reference Intakes tables provided online by the Office of Dietary Supplements.
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Can I change my B vitamin levels?
In general, your body will use the amount of B vitamins that it needs and eliminate any excess from the body. As long as an adequate amount of B vitamins are provided in the diet, blood levels will remain relatively stable. If you are deficient, your healthcare provider may want you to supplement your B vitamins but talk to your provider before taking this step.
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Should everyone have their B vitamin levels checked?
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Can B vitamins be measured at home or in my doctor's office?

Tests: Vitamin B12 and Folate
Conditions: Alcoholism, Celiac Disease, Malnutrition, Vitamin B12 Deficiency, Malabsorption
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