Laboratory tests check a sample of your blood, urine, or body tissues. A technician or your doctor analyses the test samples to see if your results fall within the normal range. The tests use a range because what is normal differs from person to person.
Many factors affect test results. These include:
Your sex, age and race
What you eat and drink
Medicines you take
How well you followed pre-test instructions
Your doctor may also compare your results to results from previous tests. Laboratory tests are often part of a routine checkup to look for changes in your health. They also help doctors diagnose medical conditions, plan or evaluate treatments, and monitor diseases.