Patient Instructions for Lab Tests
Analysis of blood and other body fluids requires special attention to appropriate patient preparation. The composition of blood is altered after meals by nutrients beign absorbed into the bloodstream. Consequently, blood drawn after a meal is not suitable for some chemistry tests. An overnight fast is preferable. This minimizes the effects of ingested substances on the test results.
It is best when blood is collected when you are in what is called a "basal" state. This means in the early morning after awakening and about 12-14 hours after the ingestion of food. When blood is not collected in the basal state, the following effects may occur:
- Moderate exercise can cause an increase in blood glucose, lactic acid, serum proteins, and creatine kinase.
- Time of Day of Collection: Diurnal variations and variations in circadian rhythm can also affect test results. For example, grouth hormone peaks in the morning before waking and decreases throughout the day. Serum iron levels may change as much as 30% to 50%, depending on individual variation, from morning until evening.
- Emotional or Physical Stress can cause variations in test results.
Fasting Tests:
If your physician tells you to "fast" before your test(s), this means that you should not have anything to eat or drink for a minimum of eight hours before the specimen is drawn. This means no juice, toast or coffee. You are able to have water while you are fasting. Consult with your physician about taking or withholding regular medications.
Click on the specific test below for patient preparation instructions.
Glucose Tolerance Test Instructions: English
Glucose Tolerance Test Instructions: Spanish
24-Hour Urine Collection Instuctions: English
24-Hour Urine Collection Instructions: Spanish
Fecal Occult Blood Test Instructions: English
Fecal Occult Blood Test Instructions: Spanish
Semen Analysis Collection Instructions: English
Semen Analysis Collection Instructions: Spanish
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