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,
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 (especially
those of Asian descent) 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 need this test if your healthcare provider wants 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 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 healthcare provider 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 healthcare provider may suggest this
if you have an ethnic background that puts you at risk.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
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 is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be 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. Be sure your healthcare
provider knows about all medicines, herbs, vitamins, and supplements you are taking.
This includes medicines that don't need a prescription and any illicit drugs you may