Insulin resistance is a clinical feature of type 2 diabetes mellitus and metabolic syndrome. In the early stages of insulin resistance, symptoms may not be apparent but when type 2 diabetes or metabolic syndrome develop symptoms may include:

• A raised blood sugar level that may cause increased thirst (polydipsia), frequent excretion of large amounts of urine (polyuria) and increased hunger (polyphagia). In addition, there may be weight gain or weight loss.
• Weakness and unexplained fatigue.
• Difficulty in concentrating and poor mental stamina - An individual may be sleepy and drowsy during the day time. This could be caused by insulin resistance or by nightly awakenings triggered by the need to urinate. Sleepiness is more pronounced after a meal that is rich in carbohydrates.
• Overweight or obesity - Consuming large amounts of carbohydrates can lead to insulin resistance and individuals with the condition may be overweight or obese. The weight gained due to insulin resistance is usually difficult to lose. Typically, the fat is stored around the abdominal organs.
• Excess carbohydrates in the diet may also cause other symptoms such as intestinal bloating, flatulence, constipation, diarrhea, nausea and vomiting.
• High blood levels of cholesterol and triglycerides. These increases may not cause overt symptoms but in, severe cases, fatty deposits around the eyes may manifest.
• Dark skin patches may be visible on parts of the neck. This is called acanthosis nigricans. Dark patches may also be present on the elbows, knuckles knees or armpits.
• The hyperglycemia seen in insulin resistance may also cause frequent genital infections, such as thrush.
• Raised blood pressure.