Dear Doctor: My nurse practitioner said I don’t need to fast before blood tests. When did that change? - oregonlive.com

ANSWER: I’ll start with the blood sugar test, the main purpose of which is to identify abnormally high glucose, either as diabetes or its precursor, prediabetes, also called borderline diabetes or impaired glucose.

Both a fasting glucose and a nonfasting glucose can give your clinician a clue, and an abnormal test would usually be followed up with a hemoglobin A1C or glucose tolerance test, which are definitive ways of diagnosing diabetes.

A nonfasting glucose is at least as good of a screening test as a fasting glucose, since fasting glucose levels are normal until the condition is pretty advanced.

Blood cholesterol is often measured as total cholesterol, HDL cholesterol, and triglycerides.

Total and HDL cholesterol are not much affected by recent meals, but triglycerides are.

Eating before a cholesterol panel usually makes the triglycerides go up, and makes the formula less accurate.

Most clinicians still prefer a fasting cholesterol, although there are good data that using non-HDL cholesterol (that’s just the total cholesterol minus the HDL cholesterol) provides as much information about a person’s heart disease risk as a fasting, calculated LDL level.

If the triglycerides themselves are very high, most clinicians will then get a fasting panel.

If a patient comes in having just eaten, a total and HDL cholesterol usually gives me all the information I need.