Over time, sugar deposits in the tiny blood vessels in the back of your eye, which are caused by chronic levels of high blood sugar, can damage the cells. To supply your eye with proper nutrients and blood flow, your body creates new blood vessels to ‘work around’ the defunct ones, explains Adrian Vella, M.D., an endocrinologist at the Mayo Clinic.

Sounds good, but there’s a problem: “These vessels are fragile and prone to breakage, leaking, and bleeding,” Vella says. In the long run, this can skew your vision, and sometimes even lead to vision loss. New blood vessels can also scar the retina, the thin layer of tissue at the back of your eye that controls vision, causing it to detach completely. If not treated immediately, this can lead to blindness, says Dr. Mathioudakis.

If you notice blurry vision or a little blob that moves in front of your line of sight, that’s a possible sign of a bleed into the eye, and you should see your doctor as soon as possible. The same applies if you’re seeing a ‘curtain’ that comes across your field of vision or a flashing light, both of which are signs of a retinal detachment.

Luckily, routine eye exams can pick up on these issues. If caught early, both laser treatments and injections into the eye can prevent further damage, says Alexander Turchin, M.D., an endocrinologist at Brigham and Women’s Hospital in Boston.

2. Numbness in your arms and/or legs.

When the small blood vessels that supply your nerves become damaged, you might feel it in the form of numbness or tingling in your feet, arms, and hands.

Think about the nerves in your body like a supply chain, says Dr. Vella. “The longest nerves in the body are the ones that are most likely to get disrupted,” he says. Those happen to be the ones that supply your limbs.

If you experience chronic numbness, tingling, or worsening shooting pains in your limbs, alert your doctor. Keep an eye out for callouses or non-healing ulcers, which, if left untreated, can eventually lead to amputation, notes Dr. Mathioudakis. That’s why it’s important for diabetics to pay extra close attention to their feet.

3. Erectile dysfunction.

To get an erection, two things need to happen: You need to have good blood flow to your member and you need to have a strong nerve signal from your brain, explains Dr. Mathioudakis. Diabetes affects both mechanisms.

In addition to vascular and nerve problems, men with diabetes often have other factors that affect sexual function, including low testosterone levels and depression or anxiety, Dr. Mathioudakis notes.

Unfortunately, if you’re struggling with diabetes, medications like Viagra — which tend to work well for general blood flow issues —don’t always perform as well, he says. In such cases, doctors will sometimes turn to injectable medications, which prove to be more potent because they’re localized.

4. Exhaustion

When your blood sugar is too high, your kidneys go into overdrive trying to filter waste from your blood. They end up working too hard, which can lead to damage down the line, according to the American Diabetes Association.

When the tiny blood vessels of the kidney get damaged, the body can’t filter out toxins very well, explains Dr. Mathioudakis. And over time, damage and scarring can lead them to fail — in which case eventually, you’d need dialysis (a treatment that performs in the place of a failing kidney) or a transplant.

Kidney dysfunction happens gradually, over a period of many years, and it can be hard to know whether you’re developing kidney damage without a blood or urine test, says Dr. Mathioudakis. But fatigue is an early symptom, which is followed in advanced stages by nausea, itching, lethargy, or confusion, notes Dr. Turchin. Even if you’re getting a normal amount of sleep, you might feel exhausted all the time for no reason.

While blood sugar control can reverse kidney damage in the early stages, it has not been shown to slow the progression of kidney disease in later stages, says Dr. Mathioudakis. “That’s why it’s so important to maintain good blood sugar control as soon as possible after being diagnosed with diabetes,” he says.

5. Chest pain or tightness.

“People with diabetes have a four-fold increased risk of cardiovascular disease,” says Mathioudakis. That’s because too much blood sugar in your blood vessels surrounding the heart can contribute to a buildup of plaque, which ultimately leads to a narrowing of the arteries—something that can lead to a heart attack.

Symptoms of coronary artery disease include pressure or tightness in the middle or left side of the chest, often triggered by exercise or emotional stress and shortness of breath, Dr. Mathioudakis says. And of course, when the arteries become completely blocked, that can lead to a heart attack.

That said, Dr. Vella notes that people with diabetes typically also have other risk factors for heart disease, too, like high cholesterol, obesity, or a sedentary lifestyle, for example. “With these, high blood sugar has additive effect,” he says.

The good news? Many of these symptoms, such as damage to the small vessels in the eyes and kidneys, are reversible. But time is of the essence. By the time you’re diagnosed with diabetes, you’ve already lost about 50 percent of function in your pancreas—the organ that creates insulin, one the main hormones that regulate blood sugar levels, he says.

So if your blood sugar readings come back high, make it your priority to get diagnosed and get your levels down.