My husband is a diabetic but is not insulin-dependent. We know what the symptoms of low blood sugar are but is there a way to recognize a high blood sugar level before it becomes too high?
You bring up a serious question regarding diabetes — that is, how can diabetics tell if their sugar is climbing above the normal level? The quick answer is that you can’t tell with any accuracy if the sugar is high. There are various symptoms that may appear when the sugar is high, and I suspect that a normally well controlled diabetic who is aware of small changes in the body might get some hints that the sugar is rising, but only hints.
As most people know, we have pretty good mechanisms for telling when the blood sugar goes too low, producing hypoglycemia. Hunger, a nervous sensation like butterflies in the stomach, and tremor all may indicate a low blood sugar. Insulin-dependent diabetics (type I) sometimes become insensitive to these early warning signs, and their blood sugar can continue to fall until they pass out or actually have a convulsion, but such insensitivity is rare in type II diabetics.
Type II diabetics can however have hypoglycemia if they are taking insulin or one of the oral drugs which stimulates insulin release from the pancreas, like glyburide or glipizide, marketed under many brand names. The new oral drugs, metformin (Glucophage), and the thioglitazones (Actos, Avandia) do not stimulate insulin release but have different mechanisms of action and rarely if ever produce hypoglycemia.
Our sensitivity to hypoglycemia probably stems from our evolutionary ancestors’ need to know when they were hungry and needed to find food. No early warning signs ever developed for too high blood sugar, or hyperglycemia, and indeed non-diabetics can have blood sugars that rise fairly high after a large carbohydrate meal. Depending on when it is taken, the blood sugar after a meal may get as high as 160 mg/dl in a non-diabetic, and we wouldn’t want to be having symptoms telling us that our sugar was rising after an occasional spaghetti binge.
The two symptoms that can indicate that the sugar is too high are frequency, the passing of more urine than usual, and blurred vision. Both of these are produced by the osmotic effect of the high sugar. When urine is formed in our kidneys, the sugar that is filtered into the urine is reabsorbed by the kidney when the blood sugar level is normal. This is obviously a benefit to us, enabling us to avoid losing the sugar and the energy that it represents. When the blood sugar is high, probably around 160 to 200 mg/dl, although the level will vary from one individual to the next, the ability of the kidney to reabsorb sugar is overwhelmed, and it starts to spill into the urine. The osmotic pressure exerted by the sugar in the urine prevents the kidneys from normally reabsorbing the water that is filtered, and the result is excess urine. Since water is being drawn out of the body in abnormal amounts, the person will quickly become dehydrated if they don’t replace the loss. The result is the excessive drinking of water that out-of-control diabetics develop.
The blurring of vision occurs because the high sugar in the blood filters into the lens of the eye. Again because of the osmotic pressure exerted by the sugar, water follows, and the lens swells, causing the blurred vision.
Unfortunately, many diabetics are quite insensitive to these symptoms of hyperglycemia, and poorly controlled diabetics may feel them all the time and consider them normal. If poorly controlled diabetics gets their eyes tested while hyperglycemic, their prescription will compensate for the hyperglycemia, and their vision will become blurred when their sugar goes down to normal. Because of this insensitivity to these symptoms, doctors have always stressed the importance of frequent routine testing of the sugar level.
When I first went into practice, we asked our diabetics to test their urine frequently for sugar. Now we have moved to the more accurate finger-prick blood tests. I will ask diabetics to test frequently, perhaps four times per day, when I am first starting them on treatment, because I want them to understand the complicated relationship between food intake, medication, exercise and blood sugar. After an effective treatment program has been worked out, I may allow them to cut back on testing to once daily, alternating between a test before breakfast, and one in the afternoon or evening.
The primary way that I monitor the long term control of my diabetic patients is actually through the hemoglobin A1c test, which provides a measure of the average blood sugar over the last three months, and therefore does not fluctuate with daily changes in food, exercise and medication in the way that the blood sugar does.
I also stress the hemoglobin A1c test because it reflects the process that I believe produces the actual bodily damage and long-term complications in diabetics. The hemoglobin A1c measures the percentage of hemoglobin A, our most common form of hemoglobin, which has had a sugar molecule attached to it. This attachment is called glycosolation and it is irreversible, meaning that there is no way to undo the sugar from the hemoglobin. But because we make new hemoglobin in our new red cells, which have a lifespan of around three months, the test in effect correlates with the average sugar level over the preceding three months. All proteins, not only hemoglobin, become glycosolated, and this tends to make the protein stiff and inflexible. One theory, which I happen to believe in, holds that this glycosolation damages the blood vessels in the body, especially in the kidneys and the eyes, causing the common diabetic complications of kidney failure and blindness.