Dextrose 5% in Water (D5W) is a sterile solution frequently administered intravenously in medical settings. This solution provides fluid for hydration and a small amount of carbohydrate to patients who cannot take fluids or nutrition by mouth. Understanding the energetic contribution of this widely used fluid is important for monitoring caloric intake. This article focuses on the precise number of calories provided by a standard 1-liter bag of D5W and its medical context.
The Direct Calorie Count and Calculation
A standard 1-liter bag of 5% Dextrose in Water provides approximately 170 kilocalories (kcal) of energy. This calculation is derived from the sugar concentration. The “5%” designation means there are 5 grams of dextrose present for every 100 milliliters (mL) of water. Since one liter equals 1,000 mL, a full liter bag of D5W contains 50 grams of dextrose.
Carbohydrates yield about 4 kcal per gram when consumed orally. However, when administered intravenously, the energy yield is slightly lower, providing approximately 3.4 kcal per gram. Multiplying the 50 grams of dextrose by 3.4 kcal/gram equals 170 kilocalories. This small number confirms that the primary function of D5W is not to provide substantial nutrition but to meet minimal energy requirements and support fluid balance.
What Exactly is Dextrose in Water?
Dextrose is the medical term for D-glucose, a simple sugar (monosaccharide) that serves as the body’s main source of energy. This sugar is the fundamental fuel metabolized by cells throughout the body, including the brain. The “water” component is highly purified, sterile water for injection, ensuring the solution is safe for direct entry into the bloodstream.
The 5% concentration makes the solution nearly isotonic with human blood plasma. Isotonic fluids have an osmolality that closely matches the concentration in the blood, which helps prevent rapid fluid shifts across cell membranes. Once the dextrose is quickly metabolized, the solution effectively becomes hypotonic, acting as free water. This allows the water to distribute easily across all fluid compartments of the body.
This free water replacement is a specific therapeutic benefit of D5W, especially when a patient needs fluid but does not require additional sodium or other electrolytes. D5W is chemically a simple carbohydrate dissolved in sterile water, formulated for safe intravenous delivery.
Medical Purpose of D5W
The low caloric count of 170 kcal per liter confirms that D5W is not intended for true nutritional support, which is measured in thousands of kilocalories per day for an adult. Instead, the solution plays a nuanced role in patient care. Its most frequent application is acting as a vehicle fluid to dilute and administer various intravenous medications. The infusion also helps maintain open intravenous access for patients requiring repeated medication doses.
Beyond functioning as a drug carrier, D5W is highly effective at replacing free water lost through insensible losses, such as breathing and sweating. The water content helps dilute the patient’s internal fluids, which is useful in treating conditions like hypernatremia (high sodium concentration in the blood).
The small carbohydrate load offers a minor benefit by preventing the body from entering a state of ketosis, which occurs during fasting or severe illness. By providing a minimal source of glucose, D5W exerts a protein-sparing action, helping minimize the breakdown of muscle protein for energy. This modest caloric provision is enough to keep basic metabolic processes running without causing a significant spike in blood sugar levels.