How Long Is Long Enough?

If you've ever undergone surgery, you probably received the traditional pre-op order: Don't eat or drink anything after midnight prior to the day of surgery. Some experts agree that the length of the recommended fast is needlessly long.

Fasting guidelines have been relaxed in recent years, but it's not uncommon for patients to be given the traditional after-midnight order. While it's always best to follow your doctor's advice, it's perfectly reasonable to ask about relaxing the fasting requirements—especially if you're scheduled for an afternoon procedure. In that case, you might be asked to go without food for more than 12 hours! Doctors and anesthesiologists are often willing to accommodate your wishes.

The after-midnight order has been the norm for decades. It's a precautionary measure to prevent pulmonary aspiration, which occurs when stomach contents enter the lungs, potentially blocking airflow and putting patients at risk for serious infections like pneumonia. However, modern anesthesia techniques make pulmonary aspiration much less likely. And when it does happen, it almost never results in long-term complications or death.

What's more, research has demonstrated that the stomach empties much faster than previously believed, and a long fasting period probably won't reduce aspiration any better than a short fast.

A long fast may add to discomfort during recovery. Fasting can lead to headaches, nausea, dizziness and dehydration. Dehydration can be serious and makes it difficult for nurses to draw blood for necessary tests.

In its preoperative fasting guidelines, the American Society of Anesthesiologists says it's safe for healthy people of all ages who undergo elective surgery to consume:

  • Clear liquids, including water, clear tea, black coffee, carbonated beverages and fruit juice without pulp, up to two hours before surgery
  • Very light meals, like toast and tea with milk, up to six hours before surgery
  • Heavy meals, including fried or fatty foods and meat, up to eight hours before surgery

Tailored fasting instructions

Despite these guidelines, don't be surprised if you schedule an elective procedure and are given after-midnight instructions. Many surgeons and hospitals continue to recommend the traditional after-midnight order on the assumption that it's easier to give everyone the same instructions. Therefore, patients don't need to count down the hours before surgery when making decisions about what to eat or drink, and health care professionals don't need to sort out which patients should have different fasting times.

Some patients do need to follow the after-midnight rule. These include people who have gastroesophageal reflux disease (GERD) and people with gastric paresis (paralysis of the stomach that can occur in people who have diabetes). These individuals have an increased risk of vomiting and aspiration during surgery and should be instructed to fast for a longer period—as should people undergoing gastric or intestinal surgeries. A blanket after-midnight order protects people who might have undiagnosed GERD or diabetes.

Source: Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50

Publication Review By: the Editorial Staff at

Published: 19 Jul 2013

Last Modified: 21 Oct 2014