Cortisol and blood sugar: how the two are linked

Cortisol is one of the hormones that help control blood sugar, so the question is a fair one. The short version is that in a stress response, and with long-term exposure to cortisol or cortisol-like medicines, glucose does go up. For ordinary diabetes risk, though, a large genetic study found no sign that cortisol levels cause type 2 diabetes.

This page separates those cases. It also covers what a cortisol test can’t do, which is diagnose diabetes.

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One blood test that shows average blood sugar over about three months.

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What cortisol does to blood sugar

MedlinePlus lists controlling blood glucose among cortisol’s jobs. It says the hormones released in stress can raise blood pressure, heart rate and blood glucose. A 2021 review calls glucocorticoids, the hormone family that includes cortisol, “catabolic hormones required to mobilize storage to provide energy”. It says short bursts of cortisol allow fast metabolic adjustments to danger or stress, whereas long-term exposure, from treatment or Cushing’s syndrome, progressively leads to insulin resistance (Int J Mol Sci, 2021).

NIDDK defines insulin resistance as a condition where the body doesn’t respond to insulin the way it should, which can raise blood glucose.

Steroid medicines and Cushing’s syndrome

Two cases are well documented.

Steroid medicine. The same review says glucocorticoid therapy is frequently associated with high blood glucose and insulin resistance, and that these drugs are the main cause of “steroid-induced diabetes”. It says up to 2 percent of diabetes cases are linked to oral or intravenous glucocorticoid therapy, with a lower link for long-term inhaled, topical or joint-injected forms. NIDDK also lists taking glucocorticoids over time among the factors that raise the chance of insulin resistance and prediabetes. If you take a steroid medicine and have concerns about your blood sugar, ask your prescriber. Don’t stop or change the dose yourself. See prednisone and cortisol.

Cushing’s syndrome. NIDDK lists insulin resistance, prediabetes and type 2 diabetes among its complications. It adds that in people with type 2 diabetes whose blood glucose stays too high over time, along with high blood pressure, Cushing’s syndrome may be the cause. It is rare, with an estimated 40 to 70 cases per million people for the kind caused inside the body, so that is a reason to ask a clinician, not a reason to assume it. See high cortisol.

Does cortisol cause type 2 diabetes?

Observational studies have linked higher cortisol to diabetes, but those can’t show which came first. A 2020 study in BMC Medicine used a different method, called Mendelian randomization, that uses gene variants that nudge cortisol levels up or down as a stand-in for cortisol itself. Genetically predicted cortisol was not associated with type 2 diabetes. It was also not associated with HbA1c, fasting glucose or fasting insulin, and diabetes did not predict cortisol either. The authors say this runs “contrary to observational studies”. They also say the gene markers for cortisol may be weak, that only one reached the usual genome-wide threshold, and that replication in a larger study is warranted (BMC Med, 2020).

So the evidence conflicts. A cortisol level in the usual range for someone with type 2 diabetes isn’t evidence of a hormone cause, and neither source supports reading one cortisol number as a diabetes risk score.

The link also runs the other way

High cortisol levels can come and go in some people, a pattern called pseudo-Cushing syndrome. MedlinePlus lists poorly controlled diabetes among its possible causes, along with depression, anxiety, alcohol use disorder and obesity. So a high cortisol result in someone with high blood sugar doesn’t mean Cushing’s syndrome. It is one more reason these results go to a clinician.

What about low blood sugar?

NIDDK lists low blood glucose (hypoglycemia) among the symptoms of adrenal insufficiency, together with long-lasting fatigue, muscle weakness, weight loss and loss of appetite. Low blood sugar has many other causes, and low cortisol is not a common one. See low cortisol for the full list of signs and the emergency symptoms.

Which test answers a blood sugar question

A cortisol test is used to help diagnose or rule out conditions of too much or too little cortisol, such as Cushing syndrome and adrenal insufficiency. It does not diagnose diabetes or prediabetes, and a single result can’t diagnose or rule out Cushing’s syndrome.

For blood sugar, two tests are common:

• A1C. MedlinePlus says it shows your average blood glucose over the past two to three months and may be used to screen for or diagnose type 2 diabetes and prediabetes.
• A blood glucose test. It shows glucose at the time of the draw. MedlinePlus says a fasting glucose test measures glucose after you fast for at least 8 hours. The seller’s page for its glucose test says fasting is required, and its page for its A1C test says it isn’t. Follow the instructions on your lab order.

• GlucoseBlood sugar at the time of the draw $28 See this test at HealthLabs

Sold by HealthLabs. Prices checked November 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.

When to see a clinician

MedlinePlus lists these symptoms of diabetes: feeling very thirsty, urinating a lot, losing weight without trying, feeling very hungry, blurred vision, and numb or tingling hands or feet. Get them checked.

A clinician can also review whether a medicine is affecting your glucose. If you take a steroid medicine, ask the prescriber how it affects blood sugar and what to watch for.

Treat vomiting you can’t stop, fainting or severe weakness as an emergency, particularly if you take a steroid medicine or have known adrenal disease. See adrenal crisis.