D5W (Dextrose 5% in Water) is a sterile intravenous (IV) fluid used in healthcare settings to provide hydration and a source of simple sugar. Administered directly into the bloodstream, this precise mixture of dextrose and sterile water serves as a vehicle for drug delivery and fluid replacement. Its primary function is to supply water to the body and address clinical needs related to blood sugar and hydration.
Decoding the Medical Name
The acronym D5W is a standardized shorthand defining the solution’s composition and concentration. The “D” stands for Dextrose, the simple sugar glucose prepared for intravenous use. The “5” represents the percentage concentration by weight, meaning there are 5 grams of dextrose for every 100 milliliters of water. The “W” indicates that the solvent is Water for injection, making D5W simply “Dextrose 5% in Water.”
This 5% concentration translates to 50 grams of dextrose per liter of fluid, providing approximately 170 calories per liter. This caloric content is not sufficient for full nutritional support. The solution itself contains no electrolytes, such as sodium or chloride, differentiating it from other common IV fluids like Normal Saline.
How the Body Processes D5W
When D5W is first infused, its concentration is similar to that of blood plasma, causing it to behave as an isotonic fluid upon immediate administration. This isotonic state is extremely short-lived once the fluid enters the body. The dextrose component is rapidly metabolized by the body’s cells, effectively removing the dissolved sugar from the bloodstream and leaving behind only sterile water.
The solution then becomes functionally hypotonic, or less concentrated than the body’s other fluids. This low concentration causes the remaining “free water” to shift out of the bloodstream and distribute across all fluid compartments, including the space inside the cells. This mechanism makes D5W an efficient way to provide pure water to the intracellular space, unlike true isotonic fluids that primarily remain in the extracellular space.
Primary Clinical Applications
D5W is commonly used as a vehicle for administering other intravenous medications. Many drugs require dilution in a sterile fluid before they can be safely infused, and D5W acts as the standard base solution for this purpose.
The fluid is also used to treat low blood sugar, or hypoglycemia, because the 5% dextrose concentration offers a ready source of glucose. Furthermore, D5W is indicated for patients with a water deficit but no corresponding loss of electrolytes, such as those with high serum sodium (hypernatremia). In these cases, the free water remaining after dextrose metabolism helps dilute the excess sodium and restore fluid balance.
Important Safety Considerations
Because D5W provides free water that distributes everywhere, rapid or excessive administration requires careful monitoring. Over-administration can lead to fluid overload, potentially resulting in pulmonary edema, where fluid builds up in the lungs. The hypotonic nature of the fluid can also cause a dangerous drop in serum sodium concentration, known as hyponatremia.
D5W is specifically avoided in patients with conditions that increase pressure inside the skull, such as cerebral edema. The free water shift into the cells can worsen brain swelling, potentially causing severe neurological complications. It must also be used cautiously in patients with known or uncontrolled diabetes, as the dextrose infusion can rapidly increase blood sugar, leading to hyperglycemia. Monitoring blood glucose and serum electrolyte levels, particularly sodium, is a requirement during administration.