If she is not on insulin, then we do really have to ask why she had hypoglycemia so profoundly to the point she required sugar therapy. That is not consistent with diabetes. Usually the sugar remains high all the time and insulin is required to treat. If you documented (by a vet or glucometer at home) last night that this was truly a weakness due to low blood sugar, then this is NOT consistent with diabetes and this makes me highly concerned she could have a pancreatic tumor called an insulinoma. Usually we see low blood sugar, not high upon initial diagnostic testing. Diagnosis of this requires a fasting glucose and insulin level. Or, low blood sugar can be associated with systemic infection.
However, what is very unusual is that she had high blood sugar initially and now low blood sugar without insulin. Tough to make sense of this being diabetes. With diabetes we see the high blood sugar; diagnosis requires a fructosamine level to confirm which must be high; if this was not done then this is another very helpful blood test (if fructosamine is high then think diabetes; if low think insulinoma). But with a diabetes mellitus dog NOT on insulin they should never have hypoglycemic episodes unless experiencing diabetic ketoacidosis (which is a medical emergency today) or systemic infection that is so profound as to cause her to have hypoglycemia but this probably would not be a one-time thing (and she'd be ill; not eating, possible persistent weakness/lethargy, etc). That means there is something else going on, and we must determine if her episode truly was hypoglycemia (was she seen at a vet and had her blood sugar tested).
If we did not confirm it was hypoglycemia last night, then her return to normal may be coincidental with administration of the sugary solution. She may have had a true faint/collapse which can come with heart arrhythmia or has another problem to cause weakness (anemia, electrolyte problem). This really does need an overall reassessment.
As a side note, we should never combine a corticosteroid (injection or oral) with a non steroidal anti-inflammatory like Rimadyl. So, if this was done and the drugs were not separated by 4-5 days from each other, then this would make me very worried. If used together, then she could have some stomach/intestinal bleeding which led to weakness. I highly recommend she have her lab work (CBC & chemistry profile) rechecked today to look at her level of red blood cells, screen for infection, screen her electrolytes and reevaluate her blood sugar; if your vet is not open then an emergency trip may be very useful especially if the emergency clinic is associated with a specialist hospital (this is a complex, not straight forward case and an internist may be very useful as a consultant).
Also, I want to mention again that it is highly uncommon for a steroid injection to bring on diabetes in a dog.
I hope that all made sense. Let me know what questions you may have.
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