Hyperglycemic syndromes cause disturbances in the tonicity of body fluids, the distribution of body water between major body fluid compartments, and the external balance of body solute and water. The unique feature of dialysis-associated hyperglycemia (DH) is that, during its development, it can cause changes exclusively in the internal balance of body solute (hypertonicity) and fluids (intracellular volume contraction and extracellular volume expansion) without affecting the external balance of water or solute. This makes DH the proper substrate for studying predictions of the changes in tonicity and extracellular volume caused by hyperglycemia because these predictions fail, by and large, to account for changes in the external balance of sodium, potassium, and water observed in hyperglycemic syndromes occurring in patients with preserved renal function. The predictions suggest that the baseline state of extracellular volume and the degree of hyperglycemia are major factors influencing the magnitude of abnormalities in the tonicity and extracellular volume resulting from DH, while transfers of solute between the intracellular compartment and the extracellular compartment have relatively smaller effects. Edematous patients are at risk for greater hypertonicity and larger increases in their extracellular volume than euvolemic -- or, even less, hypovolemic -- patients with the same degree of hyperglycemia. Studies reporting the treatment of DH with only insulin therapy can be used to test these theoretical predictions and to analyze the relationship between solute and fluid abnormalities and clinical manifestations.