hgh test blood

HGH Level Testing

Human Growth Hormone (HGH), also known as Growth Hormone (GH), is a hormone secreted by the anterior pituitary gland. Measurement of GH is primarily of interest in the diagnosis and treatment of various forms of inappropriate growth hormone secretion. The blood test is often used to evaluate a growth hormone deficiency that is causing slowed growth. It is also used to measure overall pituitary function as well as measuring replacement therapy.

If your doctor suspects that your body may be producing too much or too little GH, they will order tests to measure the levels of GH in your blood. Identifying any issues related to GH will help your doctor make a diagnosis and determine the best course of treatment for you.

GH test protocol and types

There are several different types of GH tests, and the specific testing protocol varies depending on which test your doctor orders.

As with all medical tests, it’s important to follow all of the preparation instructions from your healthcare team. In general, for GH tests your doctor will ask you to:

  • fast for a specific period of time before the test
  • stop taking the vitamin biotin, or B7, at least 12 hours before the test
  • stop taking certain prescription medications a few days before the test, if they might interfere with the test results

For some tests, your doctor may provide additional preparation instructions.

hgh level test

It’s uncommon for people to have GH levels outside the typical range, so GH tests are not performed routinely. If your doctor thinks the levels of GH in your body may be abnormal, they will likely order one or more of the following tests.

GH serum test

A GH serum test is used to measure the amount of GH in your blood when the blood is drawn. For the test, a healthcare professional will use a needle to collect a sample of your blood. The test itself is fairly routine and carries little discomfort or risk.

The blood sample will be sent to a lab for analysis. The results of a GH serum test show your doctor the level of GH in your blood at the single point in time when your blood sample was taken.

However, this may not be enough information to help your doctor make a diagnosis because levels of GH in your body naturally rise and fall throughout the day.

Insulin-like growth factor-1 test

An insulin-like growth factor-1 test (IGF-1 test) is often ordered at the same time as a GH serum test. If you have an excess or a deficiency of GH, you will also have higher- or lower-than-normal levels of IGF-1.

The key advantage of examining IGF is that, unlike GH, its levels remain stable. Only one blood sample is required for both tests.

The GH serum and IGF-1 tests don’t usually provide your doctor with enough information to make a diagnosis. These tests are usually used for screening, so that your doctor can decide if further tests are needed. If your doctor suspects that your body is producing too much or too little GH, they will likely order either a GH suppression test or a GH stimulation test.

GH suppression test

A GH suppression test helps your doctor confirm if your body produces too much GH.

For this test, a healthcare professional will use a needle or IV to take a blood sample. Then you will be asked to drink a standard solution containing glucose, a type of sugar. This will taste slightly sweet and may come in different flavors.

A healthcare professional will draw several more samples of your blood at timed intervals during the two hours after you drink the solution. These samples will be sent to a lab for analysis.

In most people, glucose lowers GH production. The lab will check your hormone levels against expected levels at each testing interval.

GH stimulation test

A GH stimulation test helps your doctor diagnose an excess or deficiency in GH production.

For this test, a healthcare professional will generally use an IV to take an initial blood sample. Then they will give you a medication that triggers your body to release GH. The healthcare professional will monitor you and take several more blood samples at timed intervals over two hours.

The samples will be sent to a lab and compared with the expected GH levels at each time point after taking the stimulant.

HGH test

Interpreting HGH test results

Your doctor will receive your lab results and interpret them. If your test results indicate that you may have a GH-related condition or if you require further testing, your doctor’s office will usually contact you for a follow-up appointment.

In general, the results of a GH serum test and an IGF-1 test don’t provide enough information to diagnose a disorder related to GH. If the results are unusual, your doctor will likely order GH suppression or stimulation tests.

If your GH level during a suppression test is high, it means that the glucose didn’t lower your GH production as expected. If your IGF-1 was also high, your doctor might diagnose an overproduction of GH. Because conditions related to growth hormone are rare and can be challenging to diagnose, your doctor might suggest additional tests.

If your hormone levels during a GH stimulation test are low, your body didn’t release as much GH as expected. If your IGF-1 level was also low, it may indicate a GH deficiency. Again, your doctor will likely recommend further testing to be certain.

Normal range for GH test results

For suppression tests, results below 0.3 nanograms per milliliter (ng/mL) are considered the normal range, according to the Mayo Clinic. Anything higher suggests that your body may be producing too much growth hormone.

For stimulation tests, a peak concentration above 5 ng/mL in children and above 4 ng/mL in adults is generally considered in the normal range.

However, the range for normal results may vary depending on the lab and your healthcare provider.

Doctor that can help to treat Growth Hormone Deficiency

hgh doctors

Because you may have various HGH deficiency causes and symptoms, your doctor will decide what kind of HGH deficiency testing to take to make sure that growth hormone deficiency test results are accurate.

To have yourself checked and diagnosed, you can approach your nearest, most trusted endocrinologist. You may check our directory of top-rated doctors who specialize in HGH deficiency so you can have yourself checked as soon as possible and get accurate results.

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