Corrective insulin is an extra shot of insulin, given in addition to the usual basal or basal/bolus dose, to overcome persistent hyperglycemia or to lower temporarily elevated blood glucose levels. In human diabetes terminology, it is known as either a corrective or correction dose because it's intended to correct the hyperglycemia. It can also be referred to as supplemental insulin, because it's in addition to the normal dose(s).  When fast or rapid-acting insulin is given regularly to manage the rise in blood glucose from meals, it is known as a bolus dose.
Corrective insulin shots in cats and dogs are not widespread practice, not recommended for beginners, and some find them too risky even for advanced use.
Occasions when extra insulin may be usefulEdit
- When exercise, infection,  or medication temporarily raises blood glucose levels. (Raising the basal dose is sometimes too risky,  but a short-term shot is more predictable and safer in some cases).
Illness places the body under stress, which can raise blood glucose levels. It also goes to work trying to rid itself of the problem; this causes some hormonal release of some of the same counter-regulatory hormones the body releases when it feels it's being threatened with hypoglycemia.  This can make it difficult to keep in good control using the same amount of insulin when there's no illness. Humans with diabetes have "sick day" plans; on those days, more insulin, more blood glucose testing and checking for ketones may be needed.
- When readjusting dosage after regulation is lost due to infection, weakened/changed insulin, or other reasons. It's safest when changing basal dose to drop the dose below the anticipated correct number, then work up very slowly. But during that readjustment time, small booster doses can keep the animal from hyperglycemia and the complications it causes.
- When the animal's current insulin dose gives good response and a low peak BG level, but not enough duration. In this case, until the insulin has "settled" and achieves greater duration or the insulin is changed, a small booster dose between shots can keep blood glucose levels in a safer range.
- Corrective insulin can also, with enough experience, be used to help diagnose the reasons behind persistent hyperglycemia after changing insulin.
Insulin Stacking can mean HypoglycemiaEdit
A hypothetical example of this would be using short-acting insulin quite soon after the usual intermediate-acting insulin has been injected. This would "stack" them; the intermediate-acting one is scheduled to peak at roughly 4-8 hours (depending on the type being used) and the short acting insulin will do the same in about 3-5 hours after it's been injected. The short-acting insulin does its part to lower the blood glucose level first. Then after it's already been lowered, the intermediate-acting one will reach peak and lower the blood glucose values even further.  The result will be a hypoglycemia incident when the intermediate-acting insulin begins acting fully without proper cautionary use of the supplemental/corrective short-acting insulin.
Another term used for this is piggybacking. 
- ↑ Your Insulin Therapy. American Family Physician (2004).
- ↑ Ketosis. Novo Nordisk.
- ↑ Diabetes Handbook. University of Massachusetts.
- ↑ When You're Sick. American Diabetes Association.
- ↑ De Witt, Dawn, Hirsch, Irl (2003). Outpatient Insulin-Supplements and Adjustments. Journal-American Medical Association.
- ↑ De Witt, Dawn, Dugdale, David (2003). Using New Insulin Strategies in the Outpatient Treatment of Diabetes-Figure 2 comments.
- ↑ De Witt, Dawn, Dugdale, David (2003). Figure 2 illustration shows both no stacking and stacking effects.
- ↑ Total Correction Dose–Insulin-On-Board-Suggested Correction Dose. Endotext.org.
- ↑ Greco, Deborah (2009). Causes of hyperglycemia and hypoglycemia in diabetic dogs. DVM 360. Archived from the original on 2013-10-16.
- ↑ Onboard Insulin. Islets of Hope.