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Renal threshold: When the blood glucose level rises over a certain level, it spills into the urine.

In diabetic contexts, the renal threshold refers to the blood glucose level at which the kidneys begin to extract glucose from the blood and excrete it into the urine, causing glycosuria.

This level varies considerably among individuals. A pet's renal threshold is usually somewhere between 180 and 270 mg/dL (10 to 15 mmol/L). Once you have determined the threshold for a given animal, it will likely remain there. The threshold is likely higher for cats than dogs -- The Animal Emergency Center of Milwaukee, WI[1] uses these renal threshold values for interpreting their lab results: dogs: 180 mg/dL, cats: 290 mg/dL. The Merck Veterinary Manual has the same 180 mg/dL value for dogs, but listes 240 mg/dL as the feline threshold[2].

Some vets use the renal threshold as an indicator of effective regulation -- reckoning that if glucose is not spilling into the urine, (easily tested using urine testing stix) the animal's blood sugar must be acceptable. This test is a good start, but this measurement is not particularly exact or reliable, and may in some cases allow organ damage to continue at high levels like 250mg/dL, which is high enough to permanently damage eyesight in dogs. Evidence from humans, mice, and in-vitro tissue studies show that damage to the pancreatic beta cells (the ones that make insulin) continues down to levels as low as 140mg/dL and a few studies show damage at levels as low as 100.[3]. The 1999 AACE guidelines[4] recommend average blood sugars (for humans) of no more than 150, preferably between 65 and 136.[5]

The converse reasoning, that an animal with glycosuria is diabetic and not well-controlled, is more accurate.

With regard to dogs, polydipsia and polyuria diabetic symptoms are not totally resolved, until he/she is kept below the renal threshold[6].


  1. Animal Emergency Center of Milwaukee-Basic Lab Values Information
  2. Merck Veterinary Manual Renal Threshold Values
  3. Research connecting organ damage with Blood Sugar level
  4. New AACE guidelines for Type-2 glucose average, 1999
  5. Conversion from HbA1c to Blood Glucose level
  6. Long-Term Management of the Diabetic Dog-2000-Drs. Fleeman & Rand-(Page 2)
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