Does this test have other names?
What is this test?
This test measures the amount of the medicine carbamazepine in your blood. Carbamazepine
is the generic name of a medicine used to treat epilepsy, mania, bipolar disorder,
and pain. Brand names include Tegretol, Carbatrol, and Equetro.
Certain people have serious but rare skin reactions during the first 4 months of taking
this medicine. Some of these reactions can be fatal. The FDA says that people at risk
for these reactions have a specific marker in their blood, HLA-B*1502, also called
the human leukocyte antigen allele. Most people who have this marker are of Asian
descent. The FDA recommends that healthcare providers screen patients for this marker
before prescribing it.
If you take this medicine for a period of time, you may also become increasingly sensitive
to its effects. This can cause the medicine to be toxic to your system. Your healthcare
provider can use this test to monitor the amount of the medicine in your body to make
sure that it doesn't reach a toxic level. Do not stop this medicine suddenly. Stopping
this medicine suddenly may cause serious problems.
Why do I need this test?
You may have this test to look at the level of carbamazepine in your body. In addition
to causing rare but serious skin and blood reactions, carbamazepine can sometimes
cause people to have suicidal thoughts.
Call your healthcare provider if you have these symptoms while taking the medicine:
Fever, sore throat, or other infections
Skin that bruises easily
Red or purple spots on the skin
Severe fatigue or weakness
Difficulty sleeping (insomnia)
Nausea, vomiting, or belly (abdominal) pain
Yellowing of the eyes or skin (jaundice)
Shortness of breath
Fast, slow, or pounding heartbeat
Any new symptoms of mental illness, including anxiety, depression, or suicidal thoughts
Any worsening of existing mental illness, including anxiety, depression, or suicidal
What other tests might I have along with this test?
Your doctor may also order other tests, including:
Liver function tests to look for liver damage
Complete blood count, with differential to find out the amount of certain types of
Electrolyte test to measure the levels of certain minerals in your blood
Blood urea nitrogen, or BUN, and creatinine tests to find out if your kidneys are
Levels of other medicines you may be taking
You may also have genetic testing before starting this medicine to find out how likely
you are to have a serious reaction to it. Your provider may suggest this if you have
an ethnic background that puts you at risk.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Results are given in micrograms per milliliter (mcg/mL) or micromoles per liter (micromol/L).
Safe blood levels of carbamazepine are 4 to 12 mcg/mL, or 17 to 51 micromol/L. You
may fall into a coma or have other health problems if your levels are above 40 mg/mL,
or 170 micromol/L.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Timing is important for this test. The most accurate results are usually from a test
done just before you take a scheduled dose of carbamazepine.
How do I get ready for this test?
Tell your healthcare provider how long you've been taking carbamazepine and what blood
level has been adequate to control your symptoms in the past. Also be sure your provider
knows about all other medicines, herbs, vitamins, and supplements you are taking.
This includes medicines that don't need a prescription and any illicit drugs you may