We lie to our dentist ("yes, I've been flossing"). We lie to our music teachers ("I practiced"). We lie to ourselves all the time ("I'm going to start that diet tomorrow"). We sometimes even lie to our spouses ("No, those pants don't make you look fat").
None of these lies are good, of course. But one of the worst lies you can do is to lie to your doctor. Three of the most common lies are:
1) Lies of Omission: This means leaving out details when briefing your doctor. Why would someone withhold information that could be valuable? Well, It can be embarrassing to expose all the intimate details of one's life even if you are speaking with someone who wants to help you. You may intentionally omit information that you think is irrelevant to the reason for your doctor visit.
2) Lies of Exaggeration: This would be telling the doctor that a condition or symptom is worse than it is. There are many reasons why a patient would do this. A patient might want to create a false sense of urgency to motivate the doctor into action. Others may want the attention that a more serious illness affords. There can be a wide array of psychological issues which are too complicated to discuss here.
3) Unintentional Lies: There are times that we simply don't remember our symptoms. It can be very difficult to accurately recall details especially if you are not feeling well. A patient may have good intentions of reporting their condition to their doctor. But instead of saying "I don't know", they make guesses or estimates that could be wildly divergent from reality.
Proper medical treatment requires clear and full communications between the patient and the provider. Your doctor needs the best information possible in order to make accurate diagnoses and treatment plans.
So.... Be honest and truthful with your doctor. If you feel that you can't do that, then it might be time to find another doctor that makes you feel more comfortable.