Bouncing is a phenomenon that occurs when the body experiences (or at least thinks it does) hypoglycemia. Luckily the body uses bouncing as a defense mechanism against this where it attempts to compensate the low blood sugar by dumping excess glucose in an attempt to raise blood sugar back to “normal” numbers. Unfortunately, “normal” is a relative term according to the body. For a diabetic whose body has been untreated for so long that it considered very high numbers to be the new normal, lower numbers can often make the body overreact in attempt to save itself, even if it’s not in danger.
A cat who has been suffering from diabetes for some time may at the point of diagnosis have a new “normal” of 400. When insulin is introduced and brings it down, even to 200 (still diabetic levels), the body thinks it is in danger, dumps excess glucose, and thus the blood sugar skyrockets up to the 400-600s. After enough time has passed, the body will eventually realize that 200 isn’t such a bad number, and bouncing will happen less often. Note some cats are extremely bounce-prone and a switch to Lantus/Levemir is needed.
There are three main causes of bouncing: when blood sugar drops too low (hypoglycemia), drops lower than the body is used too, or by dropping too much too quickly. Typically if a cat drops more than 50% of their blood sugar a bounce is likely to happen, or if they drop 100 points within an hour.
While bouncing can be considered as a safety net in the instances of hypoglycemia, it can look very confusing on paper.