D5 Water Composition
D5W (dextrose 5% in water) contains 5 grams of dextrose per 100 mL of sterile water, with no electrolytes, making it a hypotonic solution. 1
Basic Composition
Pure D5W contains only dextrose and water: 50 grams of dextrose per liter (5 g/100 mL) dissolved in sterile water with zero sodium, zero chloride, and zero other electrolytes 1
The osmolarity of pure D5W is approximately 252 mOsm/L, making it hypotonic relative to plasma (normal plasma osmolarity ~280-295 mOsm/L) 1
Common D5 Formulations with Electrolytes
D5 can be combined with various saline concentrations to create different formulations, each with distinct electrolyte content and clinical applications:
D5NS (D5 in 0.9% normal saline): Contains 50 grams dextrose plus 154 mEq/L sodium and 154 mEq/L chloride, with osmolarity of 308 mOsm/L, making it isotonic 1
D5 1/2NS (D5 in 0.45% saline): Contains 50 grams dextrose plus 77 mEq/L sodium and 77 mEq/L chloride, making it hypotonic 2
D5 0.3% saline: Contains 50 grams dextrose plus 51 mEq/L sodium and 51 mEq/L chloride, making it even more hypotonic than D5 1/2NS 2
Clinical Significance of Composition
The absence of electrolytes in pure D5W makes it fundamentally different from saline-containing formulations:
D5W provides free water without sodium load, which is why it's preferred for hypernatremic dehydration in conditions like nephrogenic diabetes insipidus where patients lose hypotonic urine 1, 3
The dextrose component is rapidly metabolized, leaving behind free water that distributes across all body compartments, effectively making it a hypotonic solution once the glucose is utilized 1
D5W as a drug diluent accounted for 21.4% of total infusion volume in ICU patients, demonstrating its widespread use as a medication vehicle beyond just fluid replacement 4
Important Compositional Considerations
Blood glucose monitoring is essential when using any dextrose-containing solution, as the 5% dextrose concentration can cause hyperglycemia, particularly in diabetic patients or those receiving large volumes 3
The tonicity is determined by sodium/potassium content, not glucose, meaning D5W remains hypotonic despite containing dextrose, which has critical implications for patients at risk of cerebral edema 2
D5W should never be administered as a bolus in patients with nephrogenic diabetes insipidus due to risk of rapid decrease in serum sodium, despite being the preferred maintenance fluid for these patients 5