3 Diabetes Tests You Must Have

Medically Reviewed by Michael Dansinger, MD on February 26, 2017
From the WebMD Archives

Mike Ellis was fly fishing when he first noticed a change in his vision. Ellis, an avid angler, had so much trouble focusing he struggled for 20 minutes before he was finally able to get a fly on his hook, something he'd done countless times over many years of fly fishing. Then, after casting his line, he was unable to see his lure on the water.

"I thought I'd scorched my eyeballs from being out in the sun too much," says Ellis, 63, a retired mechanical engineer in Denver.

An eye exam the following month revealed an equally unsettling reality: Ellis had type 2 diabetes, the most common type of the disease. Years of going undiagnosed had taken a toll on his eyesight. He had diabetic retinopathy. The blood vessels in the back of his eye were damaged, a problem that often comes with the condition.

"Diabetes damages every blood vessel in your body, including the ones in your eyes," says Robert Rizza, MD, professor of medicine at the Mayo Clinic. "Similar damage can also occur in your heart, your head, and your kidneys. But if you take care of yourself -- if you control your blood sugar, blood cholesterol, and blood pressure -- the chances of bad things happening to you are very low."

Certainly, that's the case with Ellis. With the help of three basic tests, he has his diabetes in check. These tests can help you, too.

Hemoglobin A1c Test

A simple blood test, the A1c (your doctor may call it "glycosylated hemoglobin") is done on a sample of blood taken from a finger-stick or from a small vial of it drawn from your arm. Not to be confused with the daily at-home monitoring that allows some people with diabetes to measure their blood sugars in the moment, the A1c test paints a picture of your average blood sugar level for the past 3 months.

If you can keep your hemoglobin A1c in the range of about 7% or less, you’re much less likely to have complications in your eyes, your kidneys, and your nerves, Rizza says.

When Ellis was first diagnosed, his A1c results were 7.2%. Now, after following his doctor's prescription of a healthy diet and plenty of exercise (Ellis spends 30 minutes on a stationary bike every night while he watches TV), his A1c levels are in the 6% range. Instead of having an A1c test every 3 months, the recommended norm for people with diabetes, Ellis goes in every 6 months.

"My doctor said, 'I wish everyone would follow the instructions like you do,'" he says.

Dilated Eye Exam

High blood sugar and high blood pressure can do a number on the tiny blood vessels in your eyes, but the damage can be prevented if your doctor spots it early. The best way to do that? A yearly dilated eye exam. With the help of eyedrops that enlarge your pupils for a short time, your eye doctor will examine the inside of your eyes for signs of leaky blood vessels. It's a painless test, but you won't be able to see clearly for a few hours afterward.

Ellis was diagnosed with a type of diabetic retinopathy called macular edema. It causes the leaky blood vessels that lead to swelling and blurred vision. His condition was so advanced that his eye doctor could see the bleeding in his retina without even dilating his eyes. Now he gets his eyes dilated and tested every 3 months. He also gets bi-monthly injections of a drug that blocks the leaks. He'll have to do it for the rest of his life. But it's a small price to pay.

"My ophthalmologist told me he didn't think I'd ever get my eyesight back," he says.

Foot Exam
Diabetes can also slow circulation in your feet and legs and cause you to lose feeling there. That's why the American Diabetes Association says you should get an annual foot exam.

Your doctor will check them for redness, cracks, sores, or open wounds. They'll look for weird problems (like overlapping toes); and they'll do a monofilament test. You’ll close your eyes and they'll simply press a piece of nylon to various parts of your foot. If you can’t feel it, you might have nerve damage. They may also tap on your Achilles tendon to see if the nerves on the back of your ankle are in good condition. A clue that they are? Your foot will point downward automatically.

Don't wait for a yearly exam to give your feet the once-over. Rizza suggests you check them every day at home. Wearing well-fitted shoes and socks that absorb moisture will also help.

Show Sources


Mike Ellis, retired mechanical engineer, Denver.

American Diabetes Association: “Type 2.”

CDC: “Common Eye Disorders.”

CDC: "Eat Right!"

CDC: "Stay Healthy."

National Eye Institute: “Facts About Diabetic Eye Disease?

Kellogg Eye Center: “Diabetic Retinopathy.”

American Academy of Ophthalmology: “What to Expect When Your Eyes Are Dilated."

Diabetes Forecast: “Best Treatments for Macular Edema Vision Loss.”

Lucentis product web site.

Boulton, A. Diabetes Care, August 2008.

CDC: "Vision Health Initiative."

Robert Rizza, MD, professor of medicine, division of endocrinology, diabetes, metabolism and nutrition, Mayo Clinic.

Bonora, E. Diabetes Care, May 2011.

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