What makes blood sugar levels get low?

So here’s the deal: your body doesn’t like low blood sugar anymore than you do. In fact, when everything is working “right” low blood sugars are pretty much unheard of. Your body tries to keep your blood sugar stable using a process called homeostasis.

Homeostasis is sometimes wrongly viewed as a stable state, but in fact, it's a tremendously elegant dance. The body keeps things stable by making nearly constant small adjustments.  Picture one of those old-fashioned balance scales with the chains and the plates. Like the lady justice figures hold. Imagine you have a bag of salt. The left plate is a little low, so you put a few grains on the right. Now the left plate goes a little high. So you throw a few grains on the left plate, but you over do it, and now it heads south again. So you add more to the right….

When it comes to blood sugar, the body uses insulin from the pancreas and sugar from the liver to keep your scale's plates in balance. It your sugar goes up a bit, your body pumps some insulin into the blood to lower it again. If you sugar goes down a bit, your body releases some sugar from the liver into the blood to bring it back up.

But for the blood sugar to go low, to the point where homeostasis can’t correct it, typically requires some outside interference. The most common cause of low blood sugar is too much of a blood sugar lowering medication; or a change in the circumstances surrounding the use of the medication.

If you take too much insulin, you will go low.

If you take the right amount of insulin and then eat less than you planned, you will go low.

If you take the right amount of insulin and eat exactly what you planned but are more active than usual, you will go low.

If you take the right amount of insulin and eat exactly what you planned and are not more active than usual but drink a bunch of alcohol, you will go low.

Also, medications of the sulfonylurea class cause the pancreas to overproduce insulin independent of the homeostasis mechanism, so they can force you low if you eat less, are more active, or drink more booze than usual. These meds are pills and go under the names Glyburide, Glipizide, Glucutrol, Amaryl, and the like. Prandin and Starlix, while actually a separate class of drugs, can have the same effect.

Although less common, a wide assortment of medications that are for conditions other than diabetes can also cause low blood sugar as an unintended side effect.