What is a Schilling test?
The Schilling test is a medical procedure used to determine
whether you’re absorbing vitamin B-12 properly. Your doctor may choose to order
this test if you have vitamin B-12 deficiency, or pernicious anemia.
The Schilling test usually involves up to four stages. It also involves analyzing
your urine samples to help determine the cause of the vitamin deficiency.
Your body uses vitamin B-12 to make red blood cells. Anemia
is a condition in which your body doesn’t have enough healthy red blood cells
to transport oxygen to your organs and tissues. The test is designed to measure
how well your body absorbs vitamin B-12 from your digestive tract.
Why the Schilling test is performed
Your doctor may recommend the Schilling test if you have a
vitamin B-12 deficiency. The test can help them determine whether your stomach
is producing “intrinsic factor.” Intrinsic factor is a type of protein required
for vitamin B-12 absorption. Without it, your body will be unable to absorb
vitamin B-12, resulting in pernicious anemia.
How to prepare for the Schilling test
You can’t receive any intramuscular injections of vitamin
B-12 three days before your test. Though you may drink water, you’ll need to
avoid food for eight hours before the test. You can then eat normally after the
How the Schilling test is administered
The Schilling test has four stages. After you’ve taken
enough supplements to restore a healthy level of vitamin B-12 in your system,
your doctor may advise you to undergo the test. This takes several weeks.
In stage 1, doctor will give you two doses of a vitamin B-12
supplement. The first dose will be in liquid form, which will contain a
“radiolabeled” dye that can be detected in your urine. Radiolabeling involves
using a harmless radioactive element to track a compound through your body. In
this case, your doctor tracks the dose of vitamin B-12. They can track where it
goes and how fast it gets absorbed into the body.
The second dose of vitamin B-12 is given as an injection one hour
later. These supplements alone aren’t enough to return your body’s vitamin B-12
to a healthy level. However, they can be used to test your body’s ability to absorb
Over the next 24 hours, you’ll need to collect a urine sample. You must
then bring it to your doctor’s office so your rate of vitamin B-12 absorption
can be tested. If stage 1 results are abnormal, your doctor will perform stage 2
within three to seven days.
In this stage, your doctor will give you another oral sample
of radiolabeled vitamin B-12, along with intrinsic factor. This test will show
whether a lack of intrinsic factor is the reason for your low levels of vitamin
You’ll collect a urine sample over the next 24 hours and
deliver it to your doctor to be analyzed. If the results of this test are
normal, it means you lack intrinsic factor and you most likely have pernicious
anemia. If the results are abnormal, your doctor will perform stage 3.
This test is done to see if an abnormal growth of bacteria
is causing your low vitamin B-12 levels. Before administering another dose of
radiolabeled vitamin B-12, your doctor will prescribe a two-week course of
antibiotics. If the results of this test are abnormal, they’ll perform stage 4.
This test will show your doctor if problems with your
pancreas are causing low levels of vitamin B-12. In this stage, your doctor
will give you a three-day course of pancreatic enzymes followed by a
radiolabeled dose of vitamin B-12. You’ll collect a urine sample over the
following 24 hours.
How to collect a 24-hour urine sample
On day 1, urinate into the toilet after waking up. Collect all of your
urine in a clean container for the next 24 hours.
On day 2, Urinate into the same container after getting up. Seal the
container and label it with your name and the date. Keep it refrigerated until
you can return it to your doctor.
If you need to collect a 24-hour urine sample from your
baby, follow these steps:
- Wash the area around your baby’s genitals.
- Place the urine collection bag on your baby, and
secure the adhesive tape.
- Place a diaper on your baby, covering the
- Check your baby regularly and change the bag
each time it has urine in it.
- Drain the urine into a clean container
- Deliver the container to your doctor as soon as
you’ve collected the required amount of urine.
What to expect after the Schilling test
If you have a vitamin B-12 deficiency, your doctor may perform further
tests to determine whether it’s related to any of the following factors:
Understanding the results
You have a normal test result if you urinate 8 to 40 percent
of the radiolabeled vitamin B-12 within 24 hours.
Abnormal stage 1 and
normal stage 2 results indicate that your stomach is unable to make
Abnormal stage 1 and
2 results may indicate:
- pernicious anemia
- celiac disease
- liver disease
- biliary disease
Abnormal stage 3 results
indicate that abnormal bacterial growth is causing your low levels of vitamin
Abnormal stage 4 results
indicate that problems with your pancreas are causing your low levels of
Risks of the Schilling test
In some cases, the Schilling test may produce the following minor side
- soreness at the site of the vitamin injection
- redness at the site of the vitamin injection
- mild nausea
A false-positive result occurs when the test indicates you have a
condition that you don’t have. The Schilling test may sometimes give a
false-positive result. A poor urine collection is usually the cause of this.
However, it may also happen due to kidney disease or problems with the lining
of your small intestine. You may have to take the test again if your doctor
suspects you have a false-positive result.