B Vitamins

Also Known As

Vitamin B complex

thiamine or thiamin (B1)

riboflavin (B2)

niacin (B3)

pantothenic acid (B5)

pyridoxal phosphate (B6)

biotin (B7)

Formal Name

Vitamin B Testing

This article was last reviewed on

November 9, 2015.

This article waslast modified on December 22, 2018.

At a Glance

Why Get Tested?

To screen for and detect moderate to severe vitamin B deficiencies

When To Get Tested?

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

Sample Required?

A blood sample drawn from a vein in your arm; a random or 24-hour urine sample may also be collected.

Test Preparation Needed?

Fasting is usually required for blood testing.

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

The B vitamins are nutrients that the body requires in small amounts (micronutrient) for metabolism, energy production, and for cell, skin, bone, muscle, organ, and nervous system health. B vitamin tests measure these specific compounds in the blood or urine to help evaluate a person's nutritional status.

B vitamins are absorbed from the diet, used as needed, and any excess is removed from the body through the urine. Because B vitamins are water-soluble, only small amounts are stored by the body and they must be obtained from foods rich in B vitamins or from supplements on a regular basis. Severe B vitamin deficiencies are rare in the United States but are still prevalent in areas of the world with diet deficiencies.

Deficiencies can occur when:

There is an inadequate supply of B vitamins.
Someone is unable to absorb or utilize one or more of the vitamins.
A person eats foods that inhibit the action of a vitamin.
A deficiency in another vitamin or mineral prevents its use.
The need for the vitamin is increased.

In the U.S., deficiencies are primarily seen in those with general malnutrition, chronic alcoholism, in people with malabsorption or digestive disorders, as may be seen with gastric bypass surgery and Celiac disease, and in the elderly. They are also sometimes seen with other chronic diseases, with cancer and cancer treatment, with fad diets, and with prolonged diarrhea. Pregnant women with a limited diet can be at an increased risk for B vitamin deficiencies and so can their babies. Rarely, a baby may have an inborn error of metabolism – a condition that prevents the proper use of a B vitamin.

Symptoms associated with B vitamin deficiencies can be seen in characteristic groups but may also be nonspecific, especially with mild to moderate deficiencies. Since an affected person often has multiple vitamin deficiencies, they may also have multiple symptoms. Common deficiency symptoms include a rash, dermatitis, inflamed tongue, numbness, tingling or burning in the hands or feet, anemia, fatigue, and mental changes.

B vitamin toxicity rarely occurs, usually when someone ingests much more than the recommended dose of supplements. High concentrations of a few of the B vitamins may affect the liver or nervous system.

The B vitamins include:

B1, Thiamine or thiamin

Also known as: Vitamin F, Aneurin, Thiamine diphosphate (TDP) – physiologically active form

Role: B1 is a coenzyme that helps the body produce energy, is involved in glucose, amino acid, and alcohol metabolism, and is required for the proper functioning of the nervous system, heart, and muscles.

Sources: Cereals and whole grains, potatoes, pork, seafood, nuts, legumes

Deficiency: In U.S., found primarily with chronic alcoholism. Can cause:
Wet beriberi – severe deficiency associated with cardiovascular failure
Dry beriberi – associated with nervous system, peripheral neuropathy
Wernicke's encephalopathy, Wernicke-Korsakoff syndrome – mental changes

Test name: Thiamine (Thiamine diphosphate) in blood
Other ways to measure: Transketolase (functional thiamine test)

B2, Riboflavin

Also known as: Vitamin G

Role: B2 is a coenzyme involved in energy production and is required for the metabolism of other B vitamins

Sources: Cereals and whole grains, green leafy vegetables, lean meats, dairy products, eggs, enriched breads.

Deficiency: Called ariboflavinosis, usually seen along with other vitamin deficiencies in those with alcoholism, malabsorption, liver disease, and in the elderly.

Test name: Riboflavin, blood or urine
Other ways to measure: Glutathione reductase in erythrocytes (activity)

B3, Niacin

Also known as: Nicotinic acid, Nicotinamide, Vitamin P, Vitamin PP

Role: B3 is involved in enzyme reactions, metabolism, and energy production. It is given in pharmacologic doses to lower LDL-cholesterol and triglycerides and raise HDL-cholesterol

Sources: B3 is found in lean meats, eggs, fish, whole grain cereals and legumes.

Deficiency: Severe deficiency in conjunction with a low-protein diet causes: Pellagra - classic symptoms are dermatitis, diarrhea, and dementia; may also cause a rash in areas exposed to the sun.

Deficiencies also seen with alcoholism, cirrhosis, Hartnup disease, Crohn disease, and carcinoid syndrome. Niacin synthesis requires adequate B6, B2, iron, and copper. Up to 60% of niacin is synthesized from tryptophan.

Toxicity: Pharmacologic doses can cause flushing and headaches. High doses may affect liver.

Test name: Niacin metabolites: N1-Methylnicotinamide, 2-Pyridone in urine thought to be the most reliable measure of intake and body status
Other ways to measure: measured as NAD (Nicotinamide adenine dinucleotide) in blood or urine

B5, Pantothenic acid

Role: B5 helps break down and use fats, proteins, and carbohydrates.

Sources: Most foods

Deficiency: B5 deficiency is rare as it is widely distributed in foods. Associated with "burning feet" and impaired wound healing.

Test name: Pantothenic acid in blood or urine

B6, Pyridoxal Phosphate (PLP)

Three main forms: Pyridoxine, pyridoxamine, and pyridoxal

Role: B6 is a coenzyme involved in amino acid metabolism and hemoglobin synthesis. It is also necessary for the nervous system and immune system.

Sources: Pork, fish, chicken, bananas, wheat germ, legumes.

Deficiency: B6 deficiency is rare by itself; adequate B2 is required for the formation of active PLP; may be seen with chronic alcoholism, malabsorption, smoking, and in asthmatics who take theophylline; can cause convulsions and decreased immunity. Both deficiency and toxicity can cause peripheral neuropathy.

Test name: Pyridoxal phosphate (PLP)
Other ways to measure: Vitamin B6 functional test, Urine 4-pyridoxic acid, urine xanthurenic acid

B7, Biotin

Also known as: Vitamin H, Vitamin B-w

Role: B7 is a coenzyme that is necessary for fat, protein, and carbohydrate metabolism and plays a role in hormone production.

Sources: Soy, egg yolks, peanuts, legumes, bananas, and grapefruit. B7 is also made by intestinal bacteria.

Deficiency: Very rare; may occur in those receiving total parenteral nutrition and with some inborn errors of metabolism; can cause weakness, delayed development, rash, hair loss, weakness.

Test names: Biotin in urine
Other ways to measure: Urinary 3-hydroxyisovalerate excretion

B12, Cyancobalamin

See the article on Vitamin B12 and Folate

Folic Acid or Folate

Also known as: Vitamin B9, Vitamin M
See the article on Vitamin B12 and Folate

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm. A random or 24-hour urine sample may also be collected.

Is any test preparation needed to ensure the quality of the sample?

Fasting is usually required for blood testing.

Common Questions

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.
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.
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.
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.
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.
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.
Should everyone have their B vitamin levels checked?

Most people have adequate B vitamins and will not need testing unless they develop a condition that puts them at risk of a B vitamin deficiency.
Can B vitamins be measured at home or in my doctor's office?

In general, no. These are specialized tests that need to be performed in a laboratory and may need to be sent to a reference laboratory.

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