Diabetes is a household name in this day and age. More often than not, people are concerned about their sugar intake in order to prevent diabetes. A quick Google Scholar search will reveal that a high sugar intake does not increase the risk of developing diabetes. But, of course, a chronically-high concentration of glucose in the blood will lead to a variety of problems down the line. An age-old clinical observation of diabetes is the tendency to urinate often, termed polyuria [Greek: poly (many) + ourein (to urinate)]. This is in fact where the word diabetes comes from:

Diabetes
Origin: Greek, dia- (through) + banein (to pass)
To pass through, siphon

What about the two words appended to the end of “diabetes”? They are the following:

Mellitus
Origin: Latin, mel (sweet thing)
Something sweet, honey

Insipidus
Origin: Latin, in- (without) + sapere (to have taste)
Lacking taste, in this case sweetness

Diabetes mellitus (DM) has two types, Type 1 and Type 2. The former is usually ascribed to insulin insufficiency, whereas the latter is usually ascribed to insulin resistance. It is given the name “mellitus” because of glucose in the urine, or glucosuria. The large amounts of glucose in the blood finds its way to the urine, and as a result, makes the urine—the entity being passed through—sweet. The polyuria is caused by the osmotic effect of water “following” the glucose. The quick and easy way that physicians would diagnose diabetes mellitus was to simply taste the urine of a patient suspected to have this condition.

On the contrary, diabetes insipidus (DI) is caused by a lack of water control and is not related to diabetes mellitus. This “lack of water control” involves problems with anti-diuretic hormone (ADH) production or ADH insensitivity. The former is termed central DI, since it originates in the central nervous system, and the latter is termed nephrogenic [Greek: nephros (kidney) + -genes (born from)] DI. This lack of mechanistic control stimulates profound thirst to replace the massive amounts of water lost in the urine since the water is not being reclaimed by the distal convoluted tubule and collecting duct of the nephron. However, blood glucose is not affected by this condition, there is no glucosuria, and in turn there is no sweetness in the urine—hence the urine is without taste, or “insipid.”