Here’s something that might brighten your day. “It really doesn’t matter if you’re stomach is empty” [when you have blood drawn]. Yes, that’s right; you no longer need to fast 8-12 hours and have a completely empty stomach before you have blood drawn for tests! Certainly that’s true for a lot of tests: complete blood count (CBC), electrolytes (chem-6), and most other routine blood work. Why is that? Well, for most tests, the food you eat doesn’t make a significant difference in the result you get.
No longer do you have to deal with not eating for hours, suffer with “hunger pains,” and get to the lab at the crack of dawn to wait your turn along with a horde of other patients. The one reason your doctor may want you to fast is if you’re having a lipid panel (cholesterol) or tests for diabetes (a fasting blood sugar or hemoglobin A1c). Fasting isn’t completely necessary for diabetes, though, because abnormal values for random or post-meal blood sugars have been established. Plus, hemoglobin A1c is a test for the 3-month average of blood sugar levels and eating one meal before blood is drawn won’t affect the results that much (not significantly, at least).
For a cholesterol panel, fasting does provide more accurate results, however. LDL-Cholesterol, the “bad cholesterol,” is not measured directly but is determined by a calculation using a formula* that uses the values of total cholesterol, HDL, and triglyceride levels. Having one meal before drawing a total cholesterol does not affect results. BUT triglyceride values vary greatly meal-to-meal, and can thus throw off the accuracy of LDL-C levels. For a full cholesterol panel, accuracy will be more certain if the patient fasts.
So, fasting for any blood tests, besides a blood sugar or a cholesterol panel, is no longer thought to be necessary. Temporary starvation, and all the unpleasantries attendant to that, is no longer required, and you can go to the lab any time of the day. I hope this is good news for many of you.
Reference: Lagos C. Fasting before Bloodwork is outdated for Most Patients. Medscape 2025 July 17.
* LDL-C = TC – HDL – (Trig/5)
