Having a blood sample taken may not be the most pleasant experience, but it can help you find out the status of your health and if there are problems, what you may need to do to correct them. If your doctor orders a blood test, you may have it done right there in the office or you may have to go to a lab to have your blood drawn. How you prepare for the blood test depends on which blood test you are having done. Some blood tests require virtually no advance preparation and others require you to refrain from eating and drinking certain foods and beverages. Ask your doctor about fasting for any ordered blood tests.
Blood Test for Catecholamines
Catecholamines are adrenal gland hormones that are released into your bloodstream during times of stress. They consist of epinephrine, norepinephrine and dopamine. They're usually tested via a urinalysis, but your physician may also order a blood test to check their levels. The results of a blood test for catecholamines can be skewed if you eat certain foods too close to having your blood drawn. Your physician will give you exact directions, but MedlinePlus states you need to avoiding bananas, cocoa, chocolate, citrus fruits, vanilla, coffee and tea for several days before the test; you must fast from all foods and beverages the night before the test.
Blood Test for Serotonin
You may have your serotonin levels checked if your physician suspects you have a carcinoid tumor in your digestive system or lungs. Carcinoid tumors secrete serotonin, causing the levels in your blood to become elevated. For three days prior to the blood test, St. Francis Health recommends you abstain from eating avocados, eggplant, tomatoes, plums, pineapple, walnuts, bananas, tea and coffee because these foods can interfere with the results. Ask your doctor what foods to avoid before having your serotonin levels checked.
Oral Glucose Tolerance Test
If you have diabetes or if you are to be diagnosed with diabetes, your doctor can order an oral glucose tolerance test, or OGTT. An OGTT tests your body's response to metabolizing glucose, so it's imperative that you refrain from eating any foods or beverages after midnight before having the test. During the test, you will be given a dose of glucose at certain intervals over the course of three hours, so eating or drinking anything too close to having the test performed can skew the results.
Lipid Profile
If your cholesterol and triglyceride levels are too high, you will probably have to have a lipid profile done at least once a year. A lipid profile measures the amounts of several types of cholesterol and the amount of triglycerides in your bloodstream. St. Francis Health states the test requires that you fast from all foods and beverages for 14 hours before the test in order to obtain accurate results. Your physician will advise exactly how long to fast before having blood drawn for a lipid profile.
