Below is a blood glucose curve depicting the Somogyi phenomenon. In this scenario, the positive urine glucoses prompted continued escalation in the insulin dose administered. The subsequent insulin toxicity (and concomitant hypoglycemia –or low blood glucose) resulted in initiation of protective compensatory mechanisms which caused massive transient rises in blood sugar.
In this case, urine dipsticks for glucose were checked twice daily and were always positive, prompting the owners to incrementally increase the insulin dose. This graph depicts in days what usually happens over weeks when well-meaning concerned pet owners try to use urine dipsticks to determine insulin dosing. Fortunately, the body is able to release several hormones which increase the amount of circulating glucose and which “shield” the tissues from the effects of insulin. Over time, even as the body is experiencing dramatic fluctuations in blood sugar levels, the tissues develop a resistance to insulin which may require weeks of insulin withdrawal to resolve. The best way to avoid Somogyi is to base insulin dose adjustments on blood, not urine glucose levels. Your veterinarian can do this by using a glucometer with just a drop of blood acquired every 2-3 hours for 12-24 hours, depending on how often insulin is administered.