The answer to your question depends on the type of test that your doctor
is planning on performing. For example, if your doctor is testing your blood electrolytes or blood cell counts, then you certainly can eat before the test. If your doctor is planning on looking at your blood sugar levels, then you will not be able to have any food during the day before your blood test. If your doctor is testing your cholesterol then you may or may not need to fast before your test. The older cholesterol test required that people did not eat prior to the blood draw. However, newer tests have found ways to get around this and people can eat before their blood tests. The only value that will be effected by food is your triglyceride level. If you would like an accurate reading, you may need this repeated because it won't be accurate.
I suggest that you re-schedule an appointment to see your primary care physician
. This time (to be safe) go to the appointment having not had any food. This way, you can be sure that any tests that are done are accurate. In addition, you can ask if (for future tests) it matters whether you ate or not. Good luck.