What to know about 24-hour cortisol urine tests
A doctor will usually ask someone to collect all of their urine for 24 hours, as levels of cortisol in the body change throughout the day. The doctor then sends the urine to a laboratory for testing.
This article discusses the purpose of a cortisol urine test, how a person does the test, and what the results may mean.
What are the uses of cortisol urine tests?
A person will collect their urine for 24 hours for a cortisol urine test.
Cortisol levels can change, depending on stress, injuries, infection, or health conditions.
Cortisol tests can help a doctor diagnose:
- Cushing's syndrome
- Addison disease
- conditions that affect the pituitary gland
- conditions that affect the adrenal glands
The adrenal glands produce and secrete cortisol. The hypothalamus and pituitary glands send signals to the adrenal glands about when to make cortisol and how much to make.
Cortisol is an important hormone with many functions, including stress, regulating blood glucose, and regulating blood pressure. If there is a problem with cortisol levels, people may experience a range of symptoms.
Along with urine tests, doctors can also use blood or saliva tests to measure a person's cortisol levels, depending on the situation. A urine test gives a broader picture of cortisol levels throughout the day.
High cortisol levels
If the body creates too much cortisol over a long period, a person may develop Cushing's syndrome.
Causes of high cortisol levels include:
- Long-term use of medications called glucocorticosteroids, which doctors prescribe to treat asthma, rheumatoid arthritis, and lupus.
- Tumors, especially those developing in the lungs, pituitary gland, pancreas, and thyroid.
- The excessive growth of adrenal tissues or adrenal tumors.
Low cortisol levels
Conditions that doctors associate with low cortisol levels include:
- Addison disease, where a person has underactive or damaged adrenal glands, which doctors also call primary adrenal insufficiency.
- Secondary adrenal insufficiency, where a person has an underactive pituitary gland or pituitary tumor.
- When someone stops the use of glucocorticosteroids, especially if they do this suddenly.
Who needs a cortisol urine test?
High blood pressure, or hypertension may be a sign of high cortisol levels.
Someone will normally do a 24-hour cortisol urine test if their doctor thinks their cortisol levels may be too high or too low.
People who a doctor has diagnosed with conditions such as Addison's disease or Cushing's syndrome will usually need to do regular 24-hour urine tests to monitor their treatment.
Signs and symptoms of abnormally high cortisol levels include:
- high blood pressure, or hypertension
- high blood glucose levels
- obesity, particularly in the trunk region
- thin arms and legs
- a round, flushed face
- bone weakness
- fragile skin and easy bruising
- muscle loss and weakness
- purple streaks on the abdominal region, hips, breast, or under the arms
- irregular menstrual periods and excessive facial hair
- delayed development or short stature in children
- fatty deposits between the shoulders and around the base of the neck
- increased thirst
- frequent urination
- reduced sex drive
Signs and symptoms of abnormally low cortisol levels include:
- dizziness, especially when getting up or standing
- weight loss
- muscle weakness
- low blood pressure
- dark patches of skin
- abdominal pain
- mood changes
Preparing for a urine cortisol test
A person does not need to prepare in any particular way for a urine test.
They will need to speak to a doctor if they are taking medications that can interfere with a cortisol test. These people may also need to alter medications or dosages before taking a cortisol urine test.
On the morning of the 24-hour cortisol urine test, a person will need to get up and empty their bladder into the toilet, noting the time.
From then on, they collect all the urine they produce for the rest of the day in the container the doctor provides.
People can use a small container or device, such as a toilet hat, to collect urine samples, and then carefully empty them into the larger collection container.
People should try not to get anything other than urine in the collection unit, such as feces or menstrual blood.
After 24 hours, they have to urinate one final time and add this urine to the collection. Again, they must note the time.
Some collection containers need to be refrigerated during the entire 24-hour collection period. A person will need to follow the hospital staff's instructions in this respect.
People should take the collection container to a doctor's office, hospital, or laboratory, as soon as they can after completing the test. Whoever receives the collection container will ask for the start and end times of the test.
People may need to repeat the test several times to make sure the results are accurate. A doctor may also recommend additional tests, such as blood tests, salivary tests, or dexamethasone suppression tests.
Interpreting the results
According to some reference ranges, a urinary free cortisol value for a healthy adult is between 30 and 145 nanomoles per liter over 24 hours.
However, interpreting the results of a 24-hour cortisol urine test can be tricky because average levels vary naturally between individuals.
Different organizations and health authorities use different reference ranges or cut-offs to establish whether cortisol levels are normal or abnormal.
High levels of urinary free cortisol may indicate Cushing's syndrome or a related condition. Low levels could indicate a condition such as Addison disease or secondary adrenal insufficiency.
What can affect the results?
Factors that can affect the results of 24-hour cortisol urine tests can include illnesses, infections, trauma, and obesity.
A wide range of factors can influence cortisol levels and impair the results of 24-hour cortisol urine tests.
Factors that can affect cortisol levels include:
- some diseases or illnesses
- physical and emotional stress
- cold or heat
- physical or emotional trauma
- late pregnancy
- hyperthyroidism or hypothyroidism
- medications, including contraceptives, hydrocortisone, and spironolactone
People may need to ask a doctor if drinking lots of water could affect the results of the urine test.
A doctor may order a second test if something has affected the results. People may need to wait until stress or illness has passed before doing a second test.
People taking medications that can interfere with cortisol levels should talk to their doctor about finding a safe way to measure the levels accurately. People should not stop taking a prescription medication without talking to a doctor first.
The 24-hour cortisol urine test is a simple test to check cortisol levels.
Extremely low cortisol levels cause a condition that doctors call an adrenal crisis. This can be life-threatening and requires emergency medical care.
A person must seek urgent medical attention if symptoms of adrenal crisis occur, such as:
- vomiting and diarrhea
- sudden, severe pain in the abdomen, lower back, or legs
- low blood pressure
- loss of consciousness
It is wise to speak to a doctor for any symptoms of high or low cortisol. A doctor can effectively treat many conditions that relate to high and low cortisol levels. However, long-term conditions that are not treated may become fatal.