Diabetes is a condition where the body either doesn’t produce insulin (type 1) or doesn’t use insulin properly (type 2). Both types result in too much glucose, or sugar, in the blood.

Insulin is a hormone made in the pancreas. It regulates the amount of glucose in the blood, and allows your body to use sugar from carbohydrates for energy.

Without insulin, sugar can’t get into your cells and it accumulates in the bloodstream.

About 1.5 million Americans are diagnosed with diabetes each year, yet many may remain undiagnosed.

Diabetes is a chronic, progressive illness. So understanding how to recognize symptoms is key to maintaining a healthy blood sugar level.

But early diabetes symptoms aren’t the same for everyone. Some people develop tell-tale signs of the condition, whereas others experience rare symptoms.

Here are 12 unusual symptoms that may indicate diabetes:

One possible warning sign of diabetes is the development of dark patches on your skin, particularly around your neck.

Dark patches might be widespread, or only noticeable in the creases of skin. The skin around your neck might also feel velvety or thicker.

This condition is known as acanthosis nigricans (AN). It’s sometimes present on the groin and armpits, too.

This condition is common with type 2 diabetes and in those with darker complexions. It occurs when high levels of insulin in the bloodstream cause skin cells to reproduce faster than normal.

Having diabetes can also weaken your immune system, making you more susceptible to illnesses. As a result, you may have recurrent infections.

These can include:

When there’s too much sugar in your blood, white blood cells have difficulty traveling through the bloodstream. This lowers your body’s ability to fight infections.

If you notice changes in your vision, your first thought might be to make an appointment with an eye doctor. However, vision changes may also be a warning sign of diabetes.

High blood sugar can affect every part of your body, including your eyes. It can alter fluid levels in your eyes, resulting in swelling, blurry vision, or difficulty focusing on objects.

Some people attribute lightheadedness to fatigue or hunger — which can be true — but this can also happen with diabetes, and not only with low blood sugar.

High blood sugar can cause dizziness, too. High glucose levels can trigger frequent urination, leading to dehydration. And a low level of water in your body affects how well your brain functions. Dehydration can also affect concentration and memory.

Erectile dysfunction is another possible symptom of diabetes. This typically affects males with type 2 diabetes, making it difficult for them to achieve an erection.

Sexual problems occur when high blood sugar damages nerves and the blood vessels that carry blood to the penis.

Sexual dysfunction can also occur in women, resulting in low arousal and poor lubrication. However, research on sexual issues related to diabetes in women is less conclusive than men.

Frequently feeling irritated or having changes in your mood is another sign of undiagnosed diabetes. This is because unmanaged diabetes can trigger rapid shifts in blood sugar.

You blood sugar levels can contribute to rapid shifts in mood, so levels below or above normal range can impact how you feel.

The good news is that irritability and other mood changes are temporary and emotions return to normal as blood sugar levels become more stable.

When the body doesn’t produce or can’t use insulin properly, your cells don’t get enough glucose to use for energy. As a result, the body starts burning fat and muscle mass for energy. This can cause a sudden drop in overall body weight.

Undiagnosed diabetes and blood sugar increases can also damage nerve fibers throughout your body. This damage can happen anywhere, but typically affects the nerves in the hands and feet.

This damage can cause itching. In addition, blood vessel damage caused by elevated blood sugar can reduce circulation in your limbs. This can dry out your skin leading to itching and peeling.

Fruity-smelling breath is another lesser known symptom of diabetes, or more specifically, diabetic ketoacidosis.

Again, when your body is unable to use insulin for energy, it breaks down your fat cells for energy. This process produces an acid known as ketones.

Excess ketones in the bloodstream normally leave the body through urine. Even so, when the body starts breaking down fat for energy, the effect is fruity-smelling breath or breath that smells like acetone, or nail polish.

Diabetic ketoacidosis is a severe complication of diabetes and if you believe you have it, you should seek medical attention.

When high sugar levels cause nerve damage — diabetic neuropathy — you may develop complications like pain or cramps.

This pain can occur in the legs or feet, or you may have a tingling or burning sensation or numbness in your limbs.

Anyone can have dry mouth, but it tends to affect people with diabetes because high blood sugar decreases saliva flow.

Too little saliva in the mouth is a precursor for tooth decay and gum disease. Oddly enough, dry mouth may continue even after a diabetes diagnosis. Dry mouth is a side effect of some medications used to treat diabetes.

Nausea and vomiting are other symptoms that could indicate diabetes, too. Both can occur as a result of neuropathy.

Nerve damage may prevent your body from properly moving food from the stomach to the intestines. An interruption of this process can cause food to back up in the stomach, resulting in nausea and sometimes vomiting.

Along with recognizing uncommon, rare symptoms of diabetes, it’s important to be mindful of more common symptoms associated with an inability to use insulin properly.

Common symptoms of diabetes include:

While there’s no cure for diabetes, it can be managed with a treatment plan. But if left untreated, it can lead to complications such as:

If you haven’t been feeling like yourself lately, or if you have any symptoms of diabetes, see your doctor.

A random blood sugar test, a fasting blood sugar test, and an A1C test, which measures your blood glucose over time, can help your doctor diagnose diabetes.

Once diagnosed, treatment can include insulin, oral medications, exercise, as well as dietary changes.

Early symptoms of diabetes can be hard to recognize. If you have any unusual symptoms that don’t improve or worsen, make an appointment with your doctor.

Testing can confirm or rule out this disease. If you’re diagnosed with diabetes, your doctor can recommend the best course of treatment.