Whether you're newly diagnosed with diabetes, have been managing it for years or are learning to care for someone with diabetes, knowing the basics can help make it all make sense. Here's the 101 on what happens to your body when you eat and how insulin regulates glucose
two people checking their glucose levels with a 101 written in the background
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To get an understanding of diabetes, it's helpful to know what happens when you eat, say, an apple. Through digestion, your body breaks down the apple into usable components that travel in your blood. One of these components is glucose, a form of sugar your body's cells need for fuel. But to get into most of your cells, glucose requires an escort: insulin, a hormone made in the pancreas. Think of insulin as the "key" that unlocks the door to your cells to allow glucose inside.

When all is well, beta cells in your pancreas make the correct amount of insulin whenever your blood-glucose level rises—usually after a meal—so that the glucose can get to where it's needed. But with diabetes, your body can't make enough insulin, or becomes less able to use the insulin you do make. The result? Glucose stays in the bloodstream rather than getting into the cells where it belongs, and the glucose level builds up in your blood. This condition is known as hyperglycemia, or high blood glucose.

So, what happens now? Here we'll walk you through what happens to your body and blood sugar levels when you have diabetes.

The Immediate Effects of High Blood Glucose Levels

When there's too much glucose in your blood, your body tries to compensate by drawing fluid into the blood from the tissues to dilute the concentration. This loss of fluid can cause you to become dehydrated and to feel extremely thirsty—one of the hallmark symptoms of diabetes. You might also feel terribly hungry, as your body isn't able to get enough fuel from what it eats; unplanned weight loss is a frequent result.

The problems multiply when the glucose-rich blood reaches your kidneys, whose job it is to filter out waste products and produce urine. With a higher volume of blood—and so much glucose to process—the kidneys become overwhelmed and the excess glucose "spills out" into your urine. This series of events explains why diabetes can cause you to urinate more often, and why your urine will contain excess sugar. (The phenomenon of sweet urine, in fact, is what gives diabetes its full name, diabetes mellitus—Latin for "honey.")

All these symptoms are more pronounced if you have type 1 diabetes, since the beta cells in your pancreas make little or no insulin. If you have type 2 diabetes, the symptoms may be more subtle, since you still have some insulin available—but that means diabetes is more likely to be causing problems without you being aware of them. That's why as many as one-third of people with diabetes may not even know they have it.

Longer-Term Effects of High Blood Glucose Levels

If diabetes isn't diagnosed and treated to bring blood-glucose levels under control, the long-term consequences can be serious indeed. Many of these problems are related to the body's circulation system, as glucose-heavy blood moves through blood vessels, damaging them. Most troubling is a significant increase in the risk of heart disease—already the country's number one killer—as well as a higher chance of developing high-blood pressure or strokes. Other eventualities of uncontrolled diabetes include blindness, kidney disease, nerve damage and such poor circulation that limb amputation may be necessary.

These possibilities are frightening, but there are positive actions you can take. If you stay on top of your diabetes treatment plan to manage your blood glucose as well as your blood fat and blood-pressure levels, you can cut your risks of many complications—or even avoid them altogether. And, with today's many treatment options, that's a reasonable goal.

If you are following a weight-loss program, a small amount of ketones in your blood or urine might be okay, since your body is burning up some of its fat stores. Slightly elevated ketones may simply mean you've gone too long without eating something. But high blood glucose and high ketones are a warning sign that your diabetes isn't under good control. If not treated immediately with insulin, the ketone buildup can progress to a dangerous condition called diabetic ketoacidosis, and even diabetic coma. Your diabetes care plan should include guidelines for monitoring your ketones—either by testing your blood for ketones or by dipping a test strip into your urine.

What Causes Diabetes in the First Place?

It's certainly true that you can inherit a tendency toward developing diabetes—that's one reason why it tends to run in families. Type 2 diabetes is also more common in people who belong to certain ethnic groups. But genetics apparently aren't the whole story, since many people who are predisposed to developing diabetes never do. And the incidence of type 2 diabetes, once considered a disease of adults, has climbed dramatically in the last 30 years among adults and children, even though our collective gene pool hasn't changed. Clearly, the environment in which we live plays a critical role—and that environment, experts say, has made it much easier to develop diabetes by making it all too easy to become overweight.

Call it the flip side of affluence: in recent decades food has become cheaper, more abundant and always within reach, while at the same time, computerization of our work and leisure time gives us fewer reasons to move our bodies. As a result, we're eating more, and moving less, than ever. At 3,500 calories per pound, these extra daily calories can result in a gain of 15 pounds per year! Many experts fault this so-called "obesigenic" environment for the finding that nearly two-thirds of American adults are now classified as overweight or obese.

Since both overweight and lack of exercise are key risk factors for developing diabetes, it's not surprising that the prevalence of diabetes has grown alarmingly, along with the obesity rate. Both have become epidemics.

Bottom Line: It's a Way of Life

If lifestyles can pave the way to developing diabetes, they are also some of our best means for fighting back. For many people with diabetes, lifestyle changes make all the difference. Eating better and being more physically active can have major effects on your blood-glucose levels. Staying on top of diabetes, then, is all about living well. By following healthy eating guidelines and making regular activity a part of your life, by taking medications or insulin as prescribed and by staying in touch with your diabetes care team, you are taking an active role in managing your diabetes, rather than letting it manage you.

The EatingWell Diabetes Cookbook (2005)