If you are scheduled to have surgery, recovering from surgery, or having digestive problems such as diarrhea or vomiting, your doctor may recommend that you follow a clear liquid diet, the Cleveland Clinic says. A clear liquid diet consists of foods that are easy to digest and will clear out residue in your gastrointestinal tract.

It’s a very low-calorie diet and is not meant to be followed for more than a few days. A clear liquid diet primarily consists of foods that are high in sugar, such as juice and gelatin, so people with diabetes may be concerned about how they can manage their blood sugar while on the diet.

The purpose of a clear liquid diet is to provide hydration, some minerals, and electrolytes while allowing your digestive system to rest, the Cleveland Clinic says. It also provides some calories and energy during the short period of time when you cannot eat a regular diet. The clear liquid diet is most commonly recommended before a procedure or test that requires you to have a completely empty digestive tract, such as a colonoscopy.

Managing blood sugar all or in part through diet isn’t about simply avoiding all forms of sugar, Mass General Brigham in Boston says. And it’s not just sugar in food that affects blood sugar. All foods with carbohydrates, including grains, fruit, milk, and vegetables, can increase blood sugar.

The clear liquid diet consists of liquids that are clear and melt at room temperature, the Mayo Clinic says. Many of the foods offered on the clear liquid diet are concentrated sweets, such as clear soda, clear juice such as apple or white grape, gelatin, ice pops, and honey. Other food options include hard candy, water, broth, coffee, and tea.

When following a clear liquid diet, you’ll need to monitor your blood glucose closely, and if you’re on medication, you’ll need to adjust it, according to StatPearls. While you may be used to drinking sugar-free soda and eating sugar-free gelatin, when following a clear liquid diet you need to include the regular versions of these foods to meet your daily carbohydrate needs, Hartford HealthCare in Connecticut says. They recommend eating about 15 grams of carbs per serving of clear liquid. In general, a half-cup serving of clear soda, juice, or gelatin contains 15 grams of carbohydrates, as do 1-cup servings of sports drinks, or one popsicle.

If you take medications, you’ll also need to make adjustments, according to the UMass Memorial Health–affiliated Diabetes Center of Excellence in Worcester, Massachusetts. Making sure your blood glucose levels are well-controlled is especially important before a surgery or procedure, to help reduce the risk of infection or other complications. How you’ll need to adjust your medications depends on the type of medication, how the medication is administered (pump, injection, or by mouth), and the length of time you’ll be on a clear liquid diet. You can usually return to your normal regimen once you’re cleared to eat normally again.