✍️ Written by the MedTestBD Editorial Team · Last reviewed: July 2026
What is the Serum Cortisol Test?
The serum cortisol test measures the level of cortisol — the body's primary stress hormone — in your blood. Cortisol is produced by the adrenal glands sitting above the kidneys and plays a vital role in regulating metabolism, immune response, blood pressure, and the body's reaction to stress. Because cortisol levels change significantly throughout the day, the timing of the test matters greatly.
Why is the Serum Cortisol Test Done?
- To diagnose Cushing's syndrome — a condition caused by excess cortisol, leading to weight gain, round face, and high blood sugar
- To diagnose Addison's disease — a condition caused by too little cortisol, leading to fatigue, weight loss, and low blood pressure
- To evaluate adrenal gland function
- To investigate unexplained fatigue, weakness, or abnormal blood pressure
- To monitor patients on long-term steroid therapy
Normal Serum Cortisol Levels
| Time of Test | Normal Range |
|---|---|
| Morning (8:00 AM) — peak | 6 – 23 mcg/dL (166 – 635 nmol/L) |
| Afternoon (4:00 PM) — lower | 2 – 13 mcg/dL (55 – 359 nmol/L) |
| Evening / Night — lowest | Below 5 mcg/dL |
Cortisol normally follows a diurnal rhythm — highest in the morning and lowest at night. Loss of this pattern is itself a sign of a problem. Results must always be interpreted alongside the exact time of the draw and the patient's clinical picture.
How to Prepare for the Serum Cortisol Test
- Timing is critical — the test is almost always done in the early morning around 8:00 AM when cortisol is at its peak
- Avoid heavy physical exercise, emotional stress, and caffeine before the test, as all of these raise cortisol
- Inform your doctor about any steroid medications (including inhalers or skin creams), as they affect results
- Your doctor may request a second blood draw in the afternoon for comparison
- A simple blood sample is collected from a vein in your arm
Serum Cortisol Test Price in Bangladesh
Serum cortisol test prices vary between diagnostic centers across Bangladesh. Compare serum cortisol test prices on MedTestBD →
⚠️ This information is for general reference only. Always consult a qualified physician before undergoing any medical test.
