Some tests are affected by diet, medications and supplements. Follow any test preparation instructions from your healthcare provider or the lab that will perform your test. For some tests, you may need to avoid certain medications before your sample is collected, but you should never discontinue your prescribed medications without first consulting with your health care provider. For other tests, you may need to avoid certain foods. An example is creatinine, which can be affected by eating cooked meat prior to your test.

If your results are within normal limits, it’s certainly a good sign. But one set of tests offers a snapshot of certain aspects of your health rather than a guarantee. There is a lot of overlap among results from healthy people and those with diseases, so there is still a chance that there could be an undetected problem. If you’re trying to follow a healthy lifestyle, take test results that are within range as a good sign, and keep it up. However, normal results do not mean that unhealthy habits will not have consequences in the future. Your health care provider may want to monitor you with a series of tests to make sure you’re still on track and to document any trends. A rise or drop in results, even if they are still within normal limits, could provide meaningful information.