What is a vitamin B test?

B vitamins are nutrients that your body needs to work well and stay healthy. There are eight different types. A vitamin B test checks the level of one or more B vitamins in a sample of your blood or urine (pee).

All the B vitamins together are called the "B vitamin complex." The B vitamins are:

• B1, thiamine
• B2, riboflavin
• B3, niacin (also called nicotinic acid and nicotinamide)
• B5, pantothenic acid
• B6, pyridoxal phosphate
• B7, biotin
• B9, folate (folic acid)
• B12, cobalamin

Each type of vitamin B plays different important roles in your body, such as helping to:

• Maintain normal metabolism (the process your body uses to make energy from food you eat)
• Make healthy blood cells
• Keep your nervous system working properly

You get B vitamins from many foods, including leafy green vegetables, meats and fish, eggs, whole grains, milk, and other dairy products. A lack of vitamin B is rare in the United States, because many foods have added B vitamins. These foods include cereals, breads, and pasta.

But certain diets and health conditions can affect how well your body absorbs vitamin B. And if you lack B vitamins, it can cause serious health problems. For example, a lack of B12 can cause anemia and nerve disorders.

A lack of B vitamins is called a vitamin B deficiency. It's usually treated with supplements. But it's important to talk with your health care provider before taking vitamin B supplements. That's because large amounts of some B vitamins can cause health problems, too. And some B vitamins may affect the way certain medicines work in your body.

Other names: vitamin B testing, vitamin B complex, thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxal phosphate (B6), biotin (B7), vitamin B12, folic acid, folate, and cobalamin test

What is it used for?

Vitamin B testing is used if you have symptoms that suggest you may not be getting enough of one or more B vitamins. For example, a vitamin B12 and folate test is often used for symptoms of certain types of anemia.

If you have a condition that increases your risk for a vitamin B deficiency, your provider may check your vitamin B levels even if you don't have symptoms.

Why do I need a vitamin B test?

You may need a vitamin B test if you have symptoms that could mean you're lacking certain B vitamins. The symptoms depend on which type of a vitamin B deficiency you have.

For example, common symptoms from a lack of vitamin B6 may include:

• Itchy rashes
• Cracks at the corners of the mouth
• Scaly skin on the lips
• Swollen tongue

Common symptoms from a lack of vitamin B12 may include:

• Fatigue
• Arrhythmia (problems with the rate or rhythm of your heartbeat)
• Weight loss when you're not trying to lose weight
• Tingly or numb hands and feet (a sign of nerve problems)

You may also need vitamin B testing if you have a condition or habits that increase your risk of having a vitamin B deficiency, such as:

• Celiac or Crohn's disease
• Alcohol use disorder (AUD)
• Malabsorption syndrome
• Not eating foods that are rich in B vitamins, such as animal products (meat, eggs, and/or dairy foods)
• Having had surgery on your digestive system, including gastric bypass surgery for weight loss
• Taking certain medicines that affect how your body uses certain B vitamins

What happens during a vitamin B test?

Vitamin B levels may be checked in blood or urine.

For a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

For a urine test, you may have a random urine test or a 24-hour urine sample test.

For a random urine test, you will provide a single sample of urine at any time of the day. You'll usually collect your sample at your provider's office or a lab.

For a 24-hour urine sample test, you'll need to collect all your urine during a 24-hour period. You will be given a special container to collect your urine and instructions on how to collect and store your sample. Your provider will tell you what time to start. The test generally includes the following steps:

• To begin, urinate in the toilet as usual. Do not collect this urine. Write down the time you urinated.
• For the next 24 hours, collect all your urine in the container.
• During the collection period, store the urine container in a refrigerator or cooler with ice.
• 24 hours after starting the test, try to urinate if you can. This is the last urine collection for the test.
• Return the container with your urine to your provider's office or the laboratory as instructed.

Will I need to do anything to prepare for the test?

Before a vitamin B blood test, you may need to fast (not eat or drink) for several hours before the test. A urine test doesn't require any special preparations.

Are there any risks to the test?

There is very little risk to having a blood test. You may experience slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

There is no known risk to having a urine test.

What do the results mean?

Your results will show the amount of each B vitamin that was tested. If your vitamin B levels are normal, but you have symptoms, you may need other tests to diagnose your condition.

If you're lacking in one or more B vitamins, you may need other tests to find out why. Your provider may recommend taking vitamin B supplements. In certain cases, vitamins may be given by intravenous (IV) treatment.

If you have questions about your results, talk with your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about vitamin B testing?

The meaning of vitamin B test results isn't always clear. That's because several things can affect the results, including inflammation in your body and certain medicines. And medical experts aren't sure what a normal level is for certain B vitamins. Different labs have different ranges for normal levels, too. Your provider can explain what your test results say about your health.