The cortisol test timing is very important because cortisol levels vary throughout the day. The normal range of serum cortisol levels is between 5.0 to 25.0 mcg/dL. Cortisol levels are highest during the morning hours between 6 am to 10 am and gradually fall during the day, reaching their low in the evenings between 6 pm to 11 pm and the lowest point around midnight. This is the reason why a cortisol test is advised in the morning.
Sometimes two tests are advised, one at 8 am and the other at 4 pm. The treating doctor will advise when the cortisol levels need to be checked. The test results are read either as an increased level of cortisol hormone or a decreased level of cortisol hormone.
Cortisol levels that are higher than normal could mean that:
- A tumour or excessive growth of the pituitary gland is causing your pituitary gland to release too much ACTH.
- You have an adrenal gland tumour, which causes you to produce too much cortisol.
- You have a tumour in another part of your body that affects cortisol production.
Cortisol levels that are lower than normal could mean that:
- You have Addison’s disease, which occurs when your adrenal glands produce too little cortisol.
- Hypopituitarism is a condition in which your adrenal glands produce too little cortisol as a result of the pituitary gland not sending the proper signals.
It is advisable to consult with your doctor to interpret the test reports. They may recommend more tests if the test results show that cortisol levels in your blood are too high or too low.
Disclaimer: Please consult with your doctor to interpret the test reports.