One of the most important factors in determining the accuracy and reliability of your lab test is you, the patient. After all, it is a sample from your body (blood, urine, or some other specimen) which the test will be performed. Therefore, it is essential that you do the following to ensure that the results will be useful and interpreted correctly by the doctor or practitioner and his staff:
- Follow instructions, if there are any, to prepare for the specific test you are having performed;
- Alert the person collecting your sample if you have deviated from the instructions and how;
- Inform the doctor or practitioner or another health care provider of any medications (including vitamins and supplements) you might currently be taking or foods you have eaten within the day prior to the test. If you are taking prescribed medications such as blood-thinners or seizure medication, you may want to write down the exact time at which you took your dose and when your blood was drawn. This information will be useful if your doctor has any questions about your test results.
Certain behaviors may affect some test results, such as recent or excessive exercise, not taking in enough fluids (dehydration), excessive eating, or recent sexual activity. You may be asked to refrain from some of these activities for certain tests.
It should be noted that many tests require no special preparation. But for those that do, be certain to adhere to the instructions provided. If you are ever unclear about the instructions, be sure to ask the person ordering the test for clarification. If you are not given any instructions, you should ask if there are any special instructions needed to prepare for the test.
To help you remember what you need to do before having a lab test, we will give you a written copy of instructions, if there are any. In fact, all laboratories that perform moderate and/or highly complex tests are required by the federal government under the Clinical Laboratory Improvement Amendments (CLIA) to provide patients with such written policies. You should always follow the doctor or practitioner’s instructions as the procedures for a particular test might vary.
Some of the more common types of preparation required for testing include fasting (to go without all or certain foods) for several hours before the test or even overnight. Certain tests may require you to increase or decrease the amount you drink for 10 to 12 hours prior to the test. There may be specific foods and medications you will need to avoid. Or you may be asked not to smoke before the test or even not to drink your favorite herbal tea.
Examples of some common laboratory tests that require advance preparation include:
- Glucose tolerance, fasting, two-hour post prandial blood glucose tests: fasting or eating meals at specific times may be required
- Fecal occult blood test: certain food and/or medication restrictions required
- Serum lipids (triglycerides, cholesterol, etc.): fasting for 9-12 hours is usually required