This page helps you to understand blood test results for Cortisol and gives you the reference range to determine if your lab test results mean that you have high, low or normal Cortisol levels.
We outline the risk factors associated with both raised and lower Cortisol levels.
Reference Ranges for Cortisol:
|US Conventional Units||ug/dl||5-15.5||<5 or > 15.5|
|Standard International Units||nmol/L||138-429||<138 or > 429|
What is Cortisol
Cortisol is the body’s primary stress hormone and is produced and secreted by the adrenal glands. Cortisol peaks early in the morning, then declines throughout the day, reaching its lowest level about midnight. Most cortisol in the blood is bound to a protein; only a small percentage is “free” and biologically active. Free cortisol is secreted into the urine and is present in the saliva. It is generally accepted that saliva cortisol testing is the most accurate, as it gives a better estimate of the cortisol levels within your cells, and can be done on an hourly basis to assess the pattern through the day .
Function of Cortisol
Cortisol also curbs functions that would be nonessential or detrimental in a fight-or-flight situation. It alters immune system responses and suppresses the digestive system, the reproductive system and growth processes. This complex natural alarm system also communicates with regions of your brain that control mood, motivation and fear .
Risk factors associated with Cortisol
The body’s stress-response system is usually self-limiting. Once a perceived threat has passed, hormone levels return to normal. As adrenaline and cortisol levels drop, your heart rate and blood pressure return to baseline levels, and other systems resume their regular activities.
But when stressors are always present and you constantly feel under attack, that fight-or-flight reaction stays turned on.
The long-term activation of the stress-response system — and the subsequent overexposure to cortisol and other stress hormones — can disrupt almost all your body’s processes. This puts you at increased risk of numerous health problems, including:
- Digestive problems
- Heart disease
- Sleep problems
- Weight gain
- Memory and concentration impairment 
Notable variations by demographic group
Cortisol tends to be slightly higher in women than in men. Cortisol release decreases with aging, but the blood level of this hormone stays about the same .
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Diet to improve Cortisol
The hormonal response to a low blood sugar includes a rapid release of epinephrine and glucagon, followed by a release of cortisol and growth hormone. These hormonal responses to the low blood sugar may last for 6-8 hours – during that time the blood sugar may be difficult to control. The phenomena of a low blood sugar followed by a high blood sugar is called a “rebound” or “Somogyi” reaction .
Therefore it is important to stabilise your blood sugars in order to prevent over production of cortisol. For more information on this you can look up the dietary recommendations for Glucose / Haemoglobin A1c.
Supplements for Cortisol
Vitamin C has been shown to curb levels of Cortisol while strengthening the immune system. In one study of people with high blood pressure, blood pressure and levels of cortisol returned to normal more quickly when people took vitamin C before a stressful task.
Ginseng is the most well-known adaptogen, and Asian ginseng (Panax ginseng) is considered the most potent ginseng. Research has validated Asian ginseng’s use for improving mental performance and your ability to withstand stress.
Phosphatidylserine supplementation with 600 mg per day for 10 days was shown to blunt the cortisol response to exercise-induced stress. In addition, phosphatidylserine significantly increases the testosterone to cortisol ratio. These findings suggest that phosphatidylserine is an effective supplement for combating exercise-induced stress. Phosphatidylserine supplementation promotes a desirable hormonal balance for athletes and might attenuate the physiological deterioration that accompanies overtraining .
Exercise to improve Cortisol
Besides changing your diet, one of the best stress-busting strategies is to start exercising. Aerobic exercise boosts oxygen circulation and spurs your body to make feel-good chemicals called endorphins, thereby lowering stress over the long term.
For people who have high cortisol it is advisable to stick to low intensity exercise in the short term until values are back in range as intense exercise may cause a short term increase in cortisol .
Sleep for Cortisol
Some studies have reported persistently high levels of stress hormones, particularly cortisol, in people with chronic insomnia. High levels of cortisol are associated with reduced sleep quality and reduced REM sleep.
Where cortisol is elevated, reducing cortisol levels can be a very effective approach to addressing sleep disturbances, while also reducing the long-term risks associated with elevated cortisol levels .