These symptoms may not seem related to diabetes but can mean your blood sugar is high.

More than 37 million people in the U.S. have diabetes and another 98 million have prediabetes, a condition characterized by blood sugar levels that are higher than normal but not high enough to be considered diabetes. About 2 in 10 people with diabetes don't know they have it and about 8 in 10 people are unaware they have prediabetes.

The earlier diabetes is diagnosed, the easier it is to treat. That's why recognizing signs of the condition is so important. You may already be familiar with the most obvious signs, which include increased thirst and frequent urination. But there are other subtle, and often surprising, signs of diabetes that may appear even earlier if you know what to look for. Here are some to look out for:

1. Chronic infections – When there is extra sugar in the blood, it can encourage bacteria or yeast to grow. Diabetes also impairs the immune system, making it harder for your body to fight off infections. Women with diabetes are more prone to vaginal yeast infections. You may also be more likely to get infections of the urinary tract, bladder or skin if your blood sugar is high.
2. Ongoing digestive complaints – Digestive issues like nausea, vomiting or constipation may be due to an illness or something you ate, but if symptoms linger, it could be a sign of diabetes. High blood sugar slows the digestive process, leading to these symptoms.
3. Vision problems – If you find that you need frequent changes to your eyeglass or contact lens prescription, it may be a sign of diabetes. When blood sugar levels change rapidly, it can cause the lens of your eye to swell, causing blurry or cloudy vision. Over time, untreated diabetes can also lead to serious eye conditions such as glaucoma, cataracts and blindness.
4. Skin changes – Women experiencing insulin resistance may develop acne or facial hair growth because insulin stimulates the production of male hormones. Dark, leathery patches of skin, which are most often seen on the neck, armpits or groin, are other subtle signs of high blood sugar levels.
5. Slow healing – If you have cuts or wounds that are slow to heal, it could be a sign that your blood sugar is high.
6. Unexplained weight loss – Losing weight without trying? It could be due to diabetes. When you have high blood sugar levels, the sugar is passed through your urine rather than being used for energy. This causes your body to burn fat and muscle for energy, which can result in unexpected weight loss.
7. Sexual issues – Men and women with high blood sugar levels may have a lower sex drive. Men may also experience erectile dysfunction.
8. Mental health changes – If you are prone to mood swings or feel irritable, impatient, down or fatigued, it may indicate that your blood sugar levels are not in a normal range.

Knowing if you have diabetes is important because the earlier you start treating it, the less likely you'll experience health complications due to the disease. The good news is that all it takes is a simple blood test to check your blood sugar levels. So if you have any of the symptoms listed here, talk to your doctor about being tested for diabetes.