Doctors use thick and thin blood smears to determine whether malaria-causing parasites are present in your blood. These tests should be done if you have been in a region where malaria is present, were exposed to mosquitoes, and have developed flu-like symptoms.

• A blood smear is prepared from a blood sample.
• If the first blood smear does not show the presence of malaria parasites but your doctor suspects malaria, you should have a repeat test every 8 to 12 hours for 36 hours.
• During treatment, doctors use blood smears to see whether the number of malaria parasites in the blood is decreasing.

A blood test that can diagnose malaria rapidly also is available. If this rapid test indicates a person has malaria, the results are usually confirmed with a blood smear.

Other tests

Other useful tests that may be done include:

• Liver function tests, to check for liver damage.
• Complete blood count (CBC), to check for anemia or evidence of other possible infections. Anemia sometimes develops in people with malaria, because the parasites damage red blood cells.
• A blood glucose test, to measure the amount of a type of sugar, called glucose, in your blood.

Other tests being developed to diagnose malaria include genetic tests or other blood tests that highlight parasites by using special stains. These experimental tests are not as easy to do and are not as frequently used as blood smears.

In the United States, malaria is an infectious disease that must be reported to the local or state health department.