What are Isotonic Fluids?

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  • Written By: C.B. Fox
  • Edited By: Susan Barwick
  • Last Modified Date: 27 July 2019
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There are a number of different types of intravenous (IV) fluids given to patients, the most common of which are isotonic fluids. These fluids have the same number of dissolved particles as a person’s blood. Using this type of fluid keeps extra particles from entering or exiting a patient's cells. Isotonic fluids are commonly given through an IV in order to either rehydrate a patient or to maintain his hydration level.

The most common type of isotonic fluids are 0.9% sodium chloride solutions, also referred to as normal saline fluids. The salt content of the fluids matches the normal levels in a person’s bloodstream and maintains a balance of fluid and salt between the bloodstream and the cells while the patient is being hydrated. Normal saline fluids are used to treat patients who are receiving blood transfusions, in shock, or suffering from diabetic ketoacidosis. They can be harmful to patients suffering from heart failure.

Another type of isotonic fluid that is commonly given to patients is a 5% dextrose solution. This type of isotonic fluid, often called D5W, is used in patients who are suffering from dehydration or elevated levels of salt in the blood. Patients with cardiac or renal failure can have complications from the use of these fluids.


Lactated ringer’s fluid, or LR fluid, is another type of isotonic solution and contains calcium lactate, potassium, and sodium chloride in slightly different concentrations, depending on the manufacturer. In this type of isotonic solution, however, the concentration of each of these components is low. LR fluid is used to rehydrate patients or to help those with blood or fluid loss due to disease or injury in the intestines. Patients with liver or kidney problems cannot tolerate LR fluids and require an alternative treatment.

In addition to isotonic fluids, there are hypotonic and hypertonic fluids as well. Hypotonic fluids contain fewer dissolved particles than blood, and their administration causes particles within cells to flow from the cell and into the blood. Hypertonic fluids, on the other hand, contain more dissolved particles than blood and cause cells to absorb particles in order to equalize the concentration between the cells and the bloodstream.


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Post 3

@SimpleByte - Dehydration is serious and, in extreme cases, can result in death. Kudos to your teams for taking good care of their players and helping them rehydrate after sports and exercise. Players should be monitored throughout and after games to make sure they don't show symptoms of dehydration like tiredness, dizziness, irritability, and vomiting.

Post 2

People not in the hospital getting IVs can benefit from an isotonic sports drink after intense exercise. These types of beverages replace lost fluids and electrolytes. Our local peewee football teams and little league baseball teams offer their players isotonic beverages as well as water during and after their practices and games.

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