Frequently asked questions:Excess cortisol and testing
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Cortisol and high blood sugar
Cortisol is a hormone that the body makes naturally. It helps manage stress, sleep-wake cycles, body temperature, metabolism, and blood sugar.
When there's too much cortisol in the body over a long period of time, it can keep your blood sugar high, even if you’re doing everything you can to manage your high blood sugar. This includes eating a balanced diet, exercising regularly, and taking your medications as prescribed.
Many people living with type 2 diabetes manage their blood sugar with a balanced diet, regular exercise, and medication. “Uncontrolled high blood sugar” happens when someone continues to struggle with high blood sugar no matter what they do to manage it.
Testing for excess cortisol
Your healthcare provider may be able to test your cortisol level, or they might refer you to a specialist, like an endocrinologist. You can also use this resource to help find a specialist in your area.
A DST is 1 of 3 tests available to measure cortisol levels and is the most sensitive testing option. It's also the first step to help your healthcare provider understand if a condition called Cushing syndrome (hypercortisolism) is causing your ongoing excess cortisol. Additional testing may also be necessary to confirm a diagnosis.
Once your healthcare provider decides to test your cortisol level with a DST, here’s what you can expect:
Your healthcare provider will prescribe a 1 mg dexamethasone tablet for you to take the night before you're scheduled to have your blood drawn. The tablet should be taken between 11:00 PM and 12:00 AM
The following morning, you will have your blood drawn between 8:00 AM and 9:00 AM. The blood sample will then be sent to a lab
The lab will use your blood sample to test your cortisol level, and then the results will be sent to you and your healthcare provider. Be sure to discuss the results with your healthcare provider
If your cortisol level is at or below 1.8 μg/dL, it could mean your uncontrolled high blood sugar is being caused by something else. Talk to your healthcare provider about occasionally retesting your cortisol level, as they can change over time.
If your cortisol level is higher than 1.8 μg/dL, Cushing syndrome (hypercortisolism) could be the cause of your ongoing excess cortisol. Your healthcare provider may want to run additional tests to confirm a diagnosis. Learn more about Cushing syndrome.
Information for your healthcare provider
The DST is the most sensitive testing option because it measures cortisol secretion from the adrenal gland. If you take a 1 mg dexamethasone tablet, cortisol from the adrenal gland should be suppressed. However, if your cortisol levels remain high after taking dexamethasone, it could mean the cause of excess cortisol is something from inside the body, like a growth on the adrenal or pituitary gland.
There are 3 tests that measure cortisol. The DST is the most sensitive testing option because it measures whether cortisol levels in the body can be suppressed.
According to the Endocrine Society Clinical Practice Guideline, a cortisol level greater than 1.8 μg/dL after a single dose of dexamethasone is considered a positive test.
Learn more about administering a DST.
