"Clear liquids" are any transparent drinkable liquid. Like glass, it might have color, but you should still be able to see through it. Usually they contain mostly sugar and water (except for broths and bullion, which are salty). A strict clear liquid diet excludes all solids (even noodles in soup), milk products, and citrus (orange, grapefruit) juices.

The full liquid diet is used as a step between a clear liquid diet and a regular diet. It is often used after surgery or fasting. It may be used after certain procedures, such as jaw wiring. This diet may also be appropriate for patients who have swallowing and chewing problems. The full liquid diet is low in iron, vitamin B12, vitamin A, and thiamine. It should not be used for a long period of time unless vitamins, iron, or liquid nutritional supplements are added. This diet has 1800 mg of calcium, so extra calcium is not needed.

The full liquid diet is a temporary diet that is used in several different settings. Preparation for surgery and medical tests such as sigmoidoscopy, colonoscopy, and other x-rays or tests that require little food in the stomach and intestines. When someone has been unable to eat any food for several days or after surgery. The full liquid diet helps to keep you hydrated (body fluids, salts and minerals) and helps to get the body used to food after long periods of time without food. The full liquid diet is easy to digest and does not leave much residue in the stomach and intestines.