What is a D5 (5% dextrose) solution?

What is a D5 Solution?

D5 solution is 5% dextrose in water (D5W), an intravenous fluid containing 5 grams of glucose per 100 mL (50 grams per liter) that becomes hypotonic once the dextrose is metabolized, effectively delivering free water to the body. 1

Composition and Physical Properties

• D5W contains 5 g/dL of dextrose with zero electrolytes (no sodium, potassium, chloride, calcium, or magnesium), distinguishing it from plasma which contains 135-145 mEq/L sodium 1, 2

• The osmolarity is approximately 252 mOsm/L, which appears isotonic initially but becomes hypotonic after glucose metabolism, compared to normal saline's 308 mOsm/L 2

• The dextrose component is rapidly metabolized upon infusion, leaving behind free water that distributes throughout total body water (intracellular and extracellular spaces) 3

Clinical Behavior and Distribution

• Once glucose is metabolized, D5W behaves as pure free water, distributing across all body compartments rather than remaining in the intravascular space 3

• D5W is ineffective for intravascular volume expansion because the free water component quickly leaves the vascular compartment, making it inappropriate for resuscitation or hemodynamic support 3

Primary Clinical Indications

D5W serves three main therapeutic purposes:

• Free water replacement in hypernatremia: D5W is the primary fluid for correcting elevated sodium levels because it contains no sodium and dilutes serum sodium concentration 2

• Reversing overcorrected hyponatremia: When sodium has been raised too rapidly (>8 mEq/L in 24 hours), immediately switching to D5W can lower sodium levels to prevent osmotic demyelination syndrome 2, 4

• Fluid replacement in nephrogenic diabetes insipidus: D5W matches the hypotonic urinary losses characteristic of this condition 2

Critical Safety Contraindications

D5W should be strictly avoided in several high-risk scenarios:

• Cardiac arrest and resuscitation: Dextrose-containing solutions administered during cardiac arrest greatly worsen neurologic outcomes and increase mortality, with one study showing 4 of 6 dogs receiving D5W died by 9 hours versus all surviving with lactated Ringer's 5

• Acute stroke and brain injury: Glucose can have detrimental effects in acute neurologic injury and should be avoided entirely 6

• Anaphylaxis resuscitation: Normal saline is specifically recommended as dextrose rapidly extravasates from intravascular to interstitial space 6

• Volume resuscitation needs: Any patient requiring hemodynamic support should receive isotonic crystalloids (0.9% saline or lactated Ringer's) instead 3

Common D5 Combination Solutions

D5 is frequently combined with saline solutions, creating different tonicity profiles:

• D5 0.9% NaCl (D5NS): Contains 154 mEq/L sodium and remains isotonic; this is the appropriate choice when both dextrose and isotonic fluid are needed 1, 6

• D5 0.45% NaCl (D5 half-normal): Contains 77 mEq/L sodium and is hypotonic; historically used but increasingly avoided due to hyponatremia risk in hospitalized patients 1, 6

• D5 0.3% NaCl: Contains only 51 mEq/L sodium and is even more hypotonic than D5 0.45%; this should be avoided as it poses excessive hyponatremia risk 6

• D5 lactated Ringer's: Contains 130 mEq/L sodium with balanced electrolytes and 28 mEq/L lactate buffer, providing near-isotonic fluid with dextrose 1

Monitoring Requirements When Using D5W

Close surveillance is mandatory during D5W administration:

• Check serum sodium every 2-4 hours during active correction to ensure sodium changes do not exceed 8 mEq/L in 24 hours 2

• Monitor neurological status continuously as rapid sodium shifts can cause cerebral edema or osmotic demyelination 2

• Track blood glucose levels as D5W can cause hyperglycemia, particularly in critically ill patients 7, 8

Key Clinical Pitfalls to Avoid

• Do not assume D5W is "isotonic" because it initially appears so—the glucose is rapidly metabolized, leaving hypotonic free water 3

• Do not use D5W or any dextrose-containing solution for volume resuscitation—it worsens outcomes in cardiac arrest and provides inadequate intravascular expansion 5, 3

• Do not use hypotonic dextrose solutions (D5 0.45% or D5 0.3% saline) in acutely ill hospitalized patients—they have excess antidiuretic hormone release from pain, nausea, stress, pneumonia, or CNS disorders, making them highly susceptible to dangerous hyponatremia 1, 6

• Do not use D5W as a drug diluent without considering the clinical context—switching from D5W to saline as a default diluent increases hypernatremia and hyperchloremia risk, though it doesn't affect mortality 7