Does hyperglycemia (high blood sugar) cause dehydration?

From the Guidelines

Yes, hyperglycemia can cause dehydration, as evidenced by the most recent study 1, which highlights the importance of managing hyperglycemia to prevent dehydration and other complications. When blood glucose levels are elevated, the kidneys work harder to filter and absorb the excess glucose. When the blood sugar level exceeds the renal threshold (typically around 180 mg/dL), the kidneys cannot reabsorb all the glucose, causing it to spill into the urine. This process, called osmotic diuresis, pulls water along with the glucose, resulting in increased urination (polyuria). As the body loses more fluid through frequent urination, dehydration develops if fluid intake doesn't keep pace with output. This dehydration can become severe, especially in diabetic ketoacidosis or hyperosmolar hyperglycemic state. Some key points to consider in managing hyperglycemia and preventing dehydration include:

• Initiating insulin therapy for persistent hyperglycemia above 180 mg/dL, as recommended by the most recent guidelines 1
• Targeting a glucose range of 140–180 mg/dL for most critically ill patients, and 100–180 mg/dL for noncritically ill patients, to minimize the risk of dehydration and other complications
• Ensuring adequate fluid replacement to prevent dehydration, especially in patients with hyperosmolar hyperglycemic state or diabetic ketoacidosis, as emphasized in the study 1
• Monitoring blood glucose regularly and maintaining proper hydration, especially when blood sugar levels are elevated, to prevent dehydration and other complications, as highlighted in the study 1. Symptoms of dehydration from hyperglycemia include:
• Increased thirst
• Dry mouth
• Fatigue
• Dizziness
• Decreased skin elasticity Treatment involves lowering blood glucose levels through insulin and/or oral medications as prescribed, along with adequate fluid replacement. People with diabetes should monitor their blood glucose regularly and maintain proper hydration, especially when blood sugar levels are elevated, to prevent dehydration and other complications.

From the Research

Hyperglycemia and Dehydration

• Hyperglycemia can lead to dehydration due to osmotic diuresis, which is the increased production of urine caused by high blood sugar levels 2.
• Undiagnosed or undertreated hyperglycemia may lead to electrolyte imbalance and elevated renal burden of glucose excretion, altering fluid reabsorption in the kidney and increasing the risk of dehydration 2.
• Certain antidiabetic agents used by diabetic patients may cause fluid retention/deficits and/or electrolyte abnormalities, further increasing the risk of dehydration 2.

Mechanisms of Dehydration in Hyperglycemia

• The reduction in effective insulin action combined with increased counterregulatory hormones (glucagon, catecholamines, cortisol, and growth hormone) can lead to dehydration and hyperglycemia 3.
• Dehydration can worsen the prognosis of diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic state (HHS), two serious metabolic complications of diabetes mellitus 3.
• Fasting and dehydration have differential effects on glycemia during insulin deficiency, with dehydration favoring the development of hyperglycemia and fasting resulting in reduced glucose concentrations 4.

Importance of Hydration in Hyperglycemia

• Drinking ample amounts of water and fluids with appropriate electrolyte composition is important to prevent dehydration in diabetic patients 2.
• Successful management of dehydration in patients with diabetes is crucial and can be accomplished by maintaining adequate hydration status 2.
• Reduced water intake can deteriorate glucose regulation in patients with type 2 diabetes, highlighting the importance of adequate hydration in managing hyperglycemia 5.