Cortisone (U3 Dinner) Test

Your body's main stress hormone, cortisol, is supposed to be high in the morning and low by evening. When that rhythm flattens or stays elevated late in the day, it can drive weight gain, blood sugar problems, blood pressure changes, and poor sleep, often before any standard blood test looks abnormal.

This dinner-time dried urine sample captures cortisone, the inactive form your body produces when it shuts cortisol off. Reading it alongside the other timed samples in a daily collection shows whether your stress hormone system is genuinely quieting down before bed.

What This Sample Actually Captures

Cortisone is an inactive glucocorticoid steroid hormone. Your adrenal glands make active cortisol, and an enzyme called 11-beta-HSD2 (a protein found mostly in your kidneys) converts that cortisol into cortisone. A separate enzyme called 11-beta-HSD1 (found in your liver, fat, and muscle) can switch cortisone back into active cortisol when local tissues need it. Measuring cortisone in urine therefore reflects how much cortisol your body has produced and then deactivated.

The U3 dinner sample is the third of four timed dried urine collections taken across a day. It captures what your stress hormone system is doing in the late afternoon and early evening, the window when cortisol output should be falling sharply toward its overnight low. A normal trajectory drops steeply through this window. A flat or elevated dinner reading suggests the off-switch is not working the way it should.

Why the Dinner Reading Matters

A healthy stress hormone curve is steep, not flat. Your body needs the evening drop to prepare for sleep, recovery, and overnight tissue repair. When the dinner reading stays high, it usually points to one of three things: your adrenal output is still elevated late in the day, your tissues are converting too much cortisone back into active cortisol, or your system is reacting to ongoing physical or emotional stress.

Late-day cortisol elevations also fit the pattern seen in mild forms of cortisol excess. Late-night and evening sampling of cortisone has been used as part of dexamethasone suppression testing in adrenal incidentalomas, where post-suppression salivary cortisone alone showed sensitivity of 85.3 percent and specificity of 91.7 percent for predicting serum cortisol below 50 nmol/L. The same window matters in the dried urine collection, even though the matrix is different.

Cortisol Excess and Cushing's Syndrome

In a tertiary care cohort, late-night salivary cortisone reached an area under the curve of 0.79 for Cushing's syndrome, with sensitivity around 72 percent and specificity around 86 percent. Combining late-night salivary cortisone with late-night salivary cortisol pushed the area under the curve to 0.95 for Cushing's disease, outperforming overnight dexamethasone testing alone. These data come from saliva, not dried urine, but they support the principle that evening cortisone tracks meaningful cortisol excess.

Mild autonomous cortisol secretion, also called subclinical Cushing's, often shows up first as a loss of the evening drop rather than a wildly high morning number. Hair cortisone studies have shown that people with this milder form of cortisol excess use more blood pressure medications and have worse cholesterol patterns than people with normal evening cortisone, suggesting the late-day reading carries real clinical weight.

Adrenal Insufficiency

At the other end of the spectrum, very low cortisone and cortisol throughout the day are highly specific for primary adrenal insufficiency. Home waking salivary cortisone screening in people referred for adrenal stimulation testing showed an area under the curve of 0.95 (95 percent CI 0.92 to 0.97) for diagnosing adrenal insufficiency, with negative predictive value around 96 percent and positive predictive value around 95 percent. Most of these data come from waking samples in saliva rather than dinner-time urine, but flat curves with low values across all four collection points raise the same concern in a daily dried urine profile.

Metabolic and Inflammatory Signals

Excess local activation of cortisone back into cortisol by the 11-beta-HSD1 enzyme has been observed in obesity and chronic inflammatory disease. Studies of fat tissue from women with obesity show increased 11-beta-HSD1 activity, which amplifies cortisol exposure inside fat cells even when blood cortisol looks normal. This pattern fits the metabolic syndrome picture of central weight gain, high blood sugar, and high blood pressure.

In chronic inflammatory disease such as rheumatoid arthritis, 11-beta-HSD1 activity rises as part of the body's response to inflammation, shifting the cortisol-cortisone balance and disturbing the normal daily rhythm. The dinner-time urine sample is one window into whether that shift is happening in your body.

Reference Ranges

This is a research-grade test without universally agreed cutpoints. The most useful reference data come from a 1,128-adult population study using gas chromatography mass spectrometry on urinary steroids, which established that urinary cortisone excretion varies meaningfully by sex, age, and time of day. Different labs run different assays and report in different units (most commonly nanograms per milligram of creatinine in dried urine), and your provider's lab will supply the reference range that applies to your sample.

These ranges come from a 1,128-adult European cohort using gas chromatography mass spectrometry. They are illustrative orientation for how a healthy adult curve behaves, not a target. Your lab will likely report different numbers and may use different units.

Compare your results within the same lab over time for the most meaningful trend. A single high or low number means less than the shape of your curve and how that shape changes between collections.

Tracking Your Trend

One sample is a snapshot. Stress hormone output varies day to day in response to sleep, training, illness, work pressure, and food timing. The shape of the four-point curve, especially how steeply it falls between the daytime peak and the bedtime low, is more informative than any single number.

A practical cadence: get a baseline four-point profile, then retest in 3 to 6 months if you are making targeted changes (sleep schedule, training load, stress practice), and at least annually thereafter if you are tracking adrenal health. Pay attention to whether your dinner number falls into a more normal trajectory or stays flat. The trajectory across collections is the signal.

When Results Can Be Misleading

• Collection timing errors: the U3 sample needs to be taken right before dinner, not at a random late-day moment. A sample taken too early or too late will distort the curve.
• Acute illness or surgery: any major stressor in the days before collection can elevate cortisol and cortisone temporarily across all timepoints.
• Recent intense exercise: a hard workout in the hours before collection can transiently elevate cortisol and shift the cortisone reading. Avoid intense training on collection day.
• Shift work or jet lag: if your sleep-wake cycle is disrupted, your stress hormone rhythm will be too. The reading reflects your current schedule, not your underlying biology.

What to Do With an Abnormal Result

An isolated abnormal dinner reading is rarely enough to act on alone. Pair it with the other three timepoints in your daily curve, with morning serum cortisol and ACTH if you suspect Cushing's or adrenal insufficiency, and with metabolic markers like fasting insulin, HbA1c, and a lipid panel if you suspect cortisol-driven metabolic disease. If your full curve is flat and elevated, an endocrinologist can guide further evaluation including overnight dexamethasone suppression testing. If your curve is flat and low, the next step is morning serum cortisol and an ACTH stimulation test.