A method called euglycemic clamp, the “gold standard” for determining insulin resistance, is a complicated and expensive procedure used only in a highly supervised laboratory setting. The procedure includes several injections of glucose and insulin directly into the bloodstream to determine how well cells are responding to insulin. Due to the complicated nature of this procedure, it is mainly used only in a laboratory setting to study physiological mechanisms of insulin resistance. 

Some methods used in a health care setting include measuring blood insulin levels in a fasted state. This means drawing a single blood sample in the morning prior consuming any foods or drinks. Different types of fasted state blood panels are a routine healthcare procedure during routine healthcare checkups or when suspecting illness. Insulin is not included in the standard blood panels. Typically it has to be requested separately. 

Fasting insulin levels alone are rarely used to assess insulin resistance. Instead physicians might use a special index, such as HOMA or QUICKI. These indexes have been developed to observe the balance between fasted glucose and fasting insulin. Elevated insulin, compared to glucose can be a sign of increased insulin production, which is due to insulin resistance. At the moment, there are also some hometests that are developed to measure insulin, glucose or both to determine insulin resistance based on a specific index. 

The problems with these indexes are that they are often not sensitive enough to detect early onset insulin resistance. In very early stages of insulin resistance fasting insulin can remain normal. Insulin production by the pancreas is mainly stimulated by dietary carbohydrates. In the early stages of insulin resistance, the body has to increase insulin secretion only acutely after consuming a meal. As the condition progresses insulin secretion might increase also chronically, meaning that the pancreas is secreting more insulin than normal at all times. The indexes developed to assess insulin resistance based on fasting insulin levels may therefore come at use only at this stage. 

It also seems that the threshold values of these indexes for insulin resistance can differ based on sex, age and ethnic background. It is therefore very hard to conclude insulin resistance based on this type of a single test. In addition the hometests can possess some additional problems as the samples need to be shipped to a laboratory, which may affect the quality of the home sample. 

At the moment one of the most reliable methods to detect insulin resistance in a health care setting seems to be performing an oral glucose tolerance test. This test is also used to confirm pre-diabetes or diabetes diagnosis. The difference is that when suspecting insulin resistance, in addition to blood glucose also blood insulin levels are measured. 

During an oral glucose tolerance test one is given a standardized portion of glucose solution while drawing blood samples before and typically 30 min, 60 min, 90 min and 120 min after ingestion to observe changes in glucose and insulin levels. 

At the moment there are no generally accepted threshold values to determine insulin resistance. The diagnosis is based on medical practitioners, in most cases a specialized endocrinologist, judgement. Getting a diagnosis for insulin resistance most often includes first canceling out other possible conditions that may be causing similar symptoms. Other diagnostics that may be used to support diagnosis are blood lipid profile, thyroid hormone levels and determining blood electrolyte and uric acid levels.