Not Hitting Your A1C Goals? 3 Tests To Screen for High Cortisol

You're taking your medications, watching your carbs, getting your steps in, and yet your A1C still won't decrease. One underappreciated reason may be cortisol.

Hypercortisolism, or the prolonged elevation of the stress hormone cortisol, can raise glucose levels and make it hard for people with type 2 diabetes to hit their A1C and time in range targets even if they are taking medication, exercising, and eating a healthy diet. 

Screening for, and possibly ruling out, hypercortisolism is an important step in addressing persistent high A1C levels. If hypercortisolism is confirmed, it can then be addressed. If it's not present, then other barriers to achieving glucose goals can be investigated.

Recent research has shown hypercortisolism may be more prevalent than previously thought, especially among those with type 2 diabetes whose glucose levels are not responding as expected to medication or lifestyle interventions. 

Who should get screened for hypercortisolism? 

People who have difficult-to-manage type 2 diabetes should consider asking their healthcare provider about testing for hypercortisolism, especially if they are not reaching their A1C and time in range targets, despite medications, exercise, and eating well. 

Previously, not a lot was known about hypercortisolism in relation to diabetes. However, a 2025 study showed that as many as 1 in 4 people with difficult-to-manage type 2 diabetes also have hypercortisolism, which can, in addition to affecting the ability to manage glucose levels, lead to weight gain, high blood pressure, muscle weakness, and mood changes. For those with type 2 who are taking at least three blood pressure medications, the incidence is even higher – more than 1 in 3.

Hypercortisolism exists on a spectrum. At its most severe, it becomes Cushing's syndrome, a condition typically caused by a cortisol-producing tumor or long-term steroid use, with distinctive physical signs like a rounded face, central weight gain, and purple stretch marks. 

While people with both diabetes and Cushing's often have trouble managing glucose levels, other people with difficult-to-manage diabetes may have what’s known as mild or “hidden” hypercortisolism, a form of excess cortisol that can be difficult to recognize because it lacks the classic signs of Cushing's syndrome. This absence of physical symptoms is why it’s particularly important to get screened for hypercortisolism and get treatment started as soon as possible.

Types of screening tests

There are three common tests to screen for hypercortisolism: the dexamethasone suppression test, the late-night salivary cortisol test, and the 24-hour urinary free cortisol test. None of these can definitively diagnose the condition alone, but can generally indicate if further tests are needed.

Dexamethasone suppression test

In this test, a 1 mg dose of dexamethasone (a synthetic version of cortisol) is given. The effect is that, since the adrenal glands should be able to regulate the level of cortisol in the body, the added dose should lower cortisol production, detectable in a blood or urine sample.

If cortisol levels remain high, then hypercortisolism or Cushing’s is a possible culprit, while always looking at the patient as a whole. However, the results are not conclusive and should be verified with other tests. For instance, illness, alcoholism, or stress can lead to false positives, as can hormonal birth control and estrogen. Certain types of medication, such as anti-seizure drugs, can cause cortisol levels to drop, even if the condition is present. 

Despite the risk of false positives, a 2024 study found that the DST and the late-night salivary cortisol tests (see below) are the most accurate screening tests for Cushing’s syndrome and hypercortisolism.

Late-night salivary cortisol

Except in cases of hypercortisolism or Cushing’s, cortisol production is lower at night. This test involves taking a late-night or bedtime saliva sample, often taken at home, and then having it tested in the laboratory. If cortisol levels have remained abnormally high at night, then hypercortisolism or Cushing’s is likely.

The test is simple and effective, but there is the possibility of false negative results, especially for those with lower levels of hypercortisolism, which makes the results less than definitive, researchers caution.

24-hour urinary free cortisol

In this test, urine is collected over 24 hours and tested for cortisol. Certain drugs can interfere with the results, so a medical provider may want to limit medication use during the testing time. Higher than normal levels of cortisol can suggest hypercortisolism or Cushing's. 

Because of other factors that can affect cortisol production, like medication and stress, the test may have to be administered a few times to give an accurate result. 

A recent study also found that this test may provide clinically meaningful information in people with type 2 diabetes and difficult-to-manage high blood pressure. Identifying hypercortisolism early can have significant health benefits, including improved blood pressure, reduced cardiovascular risks, and more stable blood sugar levels. It’s important to note that this test may perform better in people with more established hypercortisolism; those with mildly elevated cortisol may have normal test values.

The bottom line

While none are conclusive in themselves, these three common tests for hypercortisolism may give an indication of why you might not be reaching your A1C or time in range targets, even though you are following all the steps outlined by your healthcare team. 

It’s worth having a conversation about these tests with your healthcare provider, as they can provide a clearer picture and may lead to more targeted treatment for people with difficult-to-manage type 2 diabetes. 

Learn more about tips for managing blood sugar here:

• 6 Ways to Naturally Lower Blood Sugar
• How to Lower Morning Blood Sugar
• 8 Foods That Won't Spike Blood Sugar

This content was made possible with support from Corcept Therapeutics. Sponsored articles are independently written by diaTribe and subject to our standard editorial and medical review process to ensure they meet standards for quality, accuracy, and relevancy. Final editorial authority rests with diaTribe.