Diabetes affects 24 million people in the U.S., but only 18 million know they have it. About 90% of those people have type 2 diabetes.
In diabetes, rising blood sugar acts like a poison.
Diabetes is often called the silent killer because of its easy-to-miss symptoms. "Almost every day people come into my office with diabetes who don't know it," says Maria Collazo-Clavell, MD, an endocrinologist at the Mayo Clinic in Rochester, Minn.
The best way to pick up on it is to have a blood sugar test. But if you have these symptoms, see your doctor.
Watch the video: 5 Ways to Prevent Type 2 Diabetes
Increased urination, excessive thirst
If you need to urinate frequently—particularly if you often have to get up at night to use the bathroom—it could be a symptom of diabetes.
The kidneys kick into high gear to get rid of all that extra glucose in the blood, hence the urge to relieve yourself, sometimes several times during the night.
The excessive thirst means your body is trying to replenish those lost fluids.
These two symptoms go hand in hand and are some of "your body's ways of trying to manage high blood sugar," explains Dr. Collazo-Clavell.
Overly high blood sugar levels can also cause rapid weight loss, say 10 to 20 pounds over two or three months—but this is not a healthy weight loss.
Because the insulin hormone isn't getting glucose into the cells, where it can be used as energy, the body thinks it's starving and starts breaking down protein from the muscles as an alternate source of fuel.
The kidneys are also working overtime to eliminate the excess sugar, and this leads to a loss of calories (and can harm the kidneys). "These are processes that require a lot of energy," Dr. Collazo-Clavell notes. "You create a calorie deficit."
Excessive pangs of hunger, another sign of diabetes, can come from sharp peaks and lows in blood sugar levels.
When blood sugar levels plummet, the body thinks it hasn't been fed and craves more of the glucose that cells need to function.
Itchy skin, perhaps the result of dry skin or poor circulation, can often be a warning sign of diabetes, as are other skin conditions, such as acanthosis nigricans.
"This is a darkening of the skin around the neck or armpit area," Dr. Collazo-Clavell says. "People who have this already have an insulin resistance process occurring even though their blood sugar might not be high. When I see this, I want to check their blood sugar."
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Infections, cuts, and bruises that don't heal quickly are another classic sign of diabetes.
This usually happens because the blood vessels are being damaged by the excessive amounts of glucose traveling the veins and arteries.
This makes it hard for blood—needed to facilitate healing—to reach different areas of the body.
"Diabetes is considered an immunosuppressed state," Dr. Collazo-Clavell explains. That means heightened susceptibility to a variety of infections, although the most common are yeast (candida) and other fungal infections, she says. Fungi and bacteria both thrive in sugar-rich environments.
Women, in particular, need to watch out for vaginal candida infections.
Fatigue and irritability
"When people have high blood sugar levels, depending on how long it's been, they can get used to chronically not feeling well," says Dr. Collazo-Clavell. "Sometimes that's what brings them into the office."
Getting up to go to the bathroom several times during the night will make anyone tired, as will the extra effort your body is expending to compensate for its glucose deficiency.
And being tired will make you irritable. "We see people whose blood sugar has been really high, and when we bring the blood sugar down, it's not uncommon that I hear, ‘I didn't realize how bad I felt,'" she says.
Having distorted vision and seeing floaters or occasional flashes of light are a direct result of high blood sugar levels.
"Blurry vision is a refraction problem. When the glucose in the blood is high, it changes the shape of the lens and the eye," Dr. Collazo-Clavell explains.
The good news is that this symptom is reversible once blood sugar levels are returned to normal or near normal. But let your blood sugar go unchecked for long periods and the glucose will cause permanent damage, possibly even blindness. And that's not reversible.
Tingling or numbness
Tingling and numbness in the hands and feet, along with burning pain or swelling, are signs that nerves are being damaged by diabetes.
"If (the symptoms are) recent, it's more likely to be reversible," Dr. Collazo-Clavell says.
Still, as with vision, if blood sugar levels are allowed to run rampant for too long, neuropathy (nerve damage) will be permanent. "That's why we try to control blood sugar as quickly and as well as possible," she says.
Several tests are used to check for diabetes, but a single test result is never enough on its own to diagnose diabetes (the test has to be repeated).
One is the fasting plasma glucose test, which checks your blood sugar after a night (or eight hours) of not eating.
Blood glucose above 126 milligrams per deciliter (mg/dL) on two occasions means you have diabetes.
The normal cutoff is 99 mg/dL while a blood sugar level of 100 to 125 mg/dL is considered prediabetes, a serious condition on its own.