Myth: "If all lab reports are normal I have no disease."
Truth: If your lab reports are normal, it certainly is a good sign, but in all cases it does not mean that you have no diseases. There is a large overlap amongst the results from healthy people and those from people with diseases, so there is still a chance of an undetected problem.
Just as some healthy people’s results fall outside the reference range, lab test results in some people with disease fall within the reference range. It may also be the case that the disease may not cause any abnormality in the particular tests that you had. For example early cervical cancer won’t cause any abnormality in common blood tests but may be obvious on a Pap smear.
If you’re trying to follow a healthy lifestyle, take it as a good sign, and keep it up. But if you’re engaging in high-risk behaviour, such as drug and alcohol abuse or a poor diet, it only means "so far so good," and the potential consequences haven’t caught up with you yet. A good test result is not a licence for an unhealthy lifestyle.
Also if you have some sort of physical problems or symptoms, inspite of the normal test results, you should consult your doctor.
If you previously had abnormal results, normal results certainly provide good news. But your doctor may want to conduct follow-up tests some months later to make sure you’re still on track and to follow any trends.