HGH Testing and Diagnosis
If you suspect you have low growth hormone, the only way to know for certain is through proper testing and diagnosis. HGH testing isn’t a single test—it’s a process that includes blood work, evaluation of your symptoms, and sometimes specialized testing like the GH stimulation test. Understanding what these tests measure, why doctors use them, and what your results mean can help you move forward confidently with treatment decisions.
Why HGH Testing Matters
Testing your growth hormone levels is essential because low GH causes symptoms that could be caused by many other things. Fatigue, weight gain, and low libido could indicate low thyroid, vitamin deficiency, depression, or dozens of other conditions. The only way to know if low growth hormone is actually your problem is through testing.
Testing also helps your doctor determine the right treatment approach. If your growth hormone is actually normal, HGH therapy won’t help—and won’t be prescribed. If it’s low, testing shows how low, which guides your doctor in determining the appropriate starting dose.
Finally, testing provides a baseline for comparison. Once you start HGH therapy, your doctor will retest periodically to make sure your levels are in the target range and that your treatment is working as expected.
Why Doctors Test IGF-1 Instead of HGH Directly
You might wonder why your doctor orders an IGF-1 test instead of directly measuring growth hormone. The reason is practical and scientific:
- HGH fluctuates throughout the day: Growth hormone is released in pulses, especially during sleep and exercise. A single blood test for HGH might show high levels right after exercise or low levels at other times. This makes direct GH testing unreliable for diagnosis.
- IGF-1 is stable: Insulin-like growth factor 1 (IGF-1) doesn’t fluctuate hourly like GH does. It reflects your average growth hormone production over the past several weeks. A single IGF-1 blood test gives a reliable snapshot of your overall growth hormone status.
- IGF-1 does the real work: Most of the effects you associate with growth hormone—muscle growth, fat loss, skin quality, bone strength—are actually caused by IGF-1, not GH directly. GH triggers IGF-1 production, and IGF-1 does the heavy lifting. Testing IGF-1 tells your doctor whether the growth hormone in your system is actually working.
- Clinical correlation: Decades of medical research have established what IGF-1 levels should be for each age and sex. Your doctor compares your results to these established ranges to determine if you have low growth hormone.
This is why IGF-1 testing is the gold standard for evaluating growth hormone status.
What the IGF-1 Test Measures
IGF-1 is a hormone produced primarily in the liver in response to growth hormone stimulation. When your pituitary releases growth hormone, it travels to your liver and triggers IGF-1 production. IGF-1 then travels throughout your body, causing the effects associated with growth hormone: muscle growth, fat loss, improved bone density, better skin quality, and other benefits.
Your IGF-1 level reflects how much growth hormone your body is producing on average. Low IGF-1 means low growth hormone production. High IGF-1 means high growth hormone production. Normal IGF-1 means your growth hormone is in the healthy range.
Normal IGF-1 levels vary significantly by age. Children and young adults have the highest levels (200-500 ng/mL is typical). Levels decline with age. By age 60, normal IGF-1 might be 100-250 ng/mL. Your doctor compares your result to the normal range for your age to determine if you have low growth hormone.
The GH Stimulation Test
In some cases, your doctor might order a GH stimulation test, especially if your IGF-1 is borderline low or if you have a suspected pituitary disorder. This test involves:
- Baseline blood draw: Blood is drawn to measure your resting growth hormone level.
- Stimulation: You receive an injection or oral dose of a medication that stimulates growth hormone release. Common stimulators include insulin, glucagon, or L-arginine.
- Timed blood draws: Blood is drawn at specific intervals (usually 15, 30, 45, and 60 minutes after stimulation) to measure how your pituitary responds.
- Analysis: Your doctor looks at whether your GH levels rise appropriately in response to stimulation. A healthy pituitary should show a significant rise. An inadequate rise suggests growth hormone deficiency.
This test is more definitive than simple IGF-1 testing because it directly measures your pituitary’s ability to produce growth hormone. However, it’s more involved and less commonly needed. Most diagnoses are made using IGF-1 testing alone.
Understanding Your Results
When you get your IGF-1 test results, your report will show:
- Your IGF-1 level: The numerical value, usually in ng/mL (nanograms per milliliter).
- The normal range: What’s considered normal for your age and sex.
- Whether you’re low, normal, or high: Some reports clearly state this; others you have to interpret based on comparing your number to the range.
Low IGF-1 levels (below the normal range for your age) suggest growth hormone deficiency. If your IGF-1 is low and you have symptoms consistent with low GH, your doctor will likely recommend HGH therapy.
Normal or high IGF-1 means your growth hormone is adequate, and HGH therapy probably won’t help.
Your doctor will discuss your results with you and explain what they mean for your health and treatment options.
How to Get Tested
Getting tested starts with a consultation with a National HRT doctor to discuss your symptoms. If testing is appropriate, we schedule blood work at a partner laboratory near you. Our doctor reviews your results and discusses your options—if IGF-1 is low and you’re symptomatic, treatment options are discussed. If your levels are normal, we help determine what else might be causing your symptoms. The entire process takes 1-2 weeks.
If you qualify for treatment, see our guide on how to get an HGH prescription for the full process.
FAQs
How is growth hormone deficiency diagnosed?
Growth hormone deficiency is diagnosed through a combination of clinical evaluation and blood testing. Your doctor reviews your symptoms (fatigue, weight gain, muscle loss, low libido, poor sleep), medical history, and physical findings. Blood work—primarily IGF-1 testing—shows whether your growth hormone production is low. If your IGF-1 is below the normal range for your age and your symptoms match low GH, your doctor diagnoses growth hormone deficiency. Additional tests like a GH stimulation test may be ordered if the diagnosis is unclear.
What is a normal IGF-1 level?
Normal IGF-1 levels vary by age. Young adults typically have IGF-1 levels of 200-500 ng/mL. Levels decline gradually with age. A 40-year-old might have a normal range of 100-300 ng/mL, while a 60-year-old’s normal range might be 50-200 ng/mL. Your lab report will show what’s normal for your specific age. Your doctor compares your result to this age-adjusted normal range to determine if you have low growth hormone.
Do I need to fast before an IGF-1 test?
Most doctors recommend fasting before HGH testing—usually 8-12 hours of no food, just water. However, IGF-1 itself isn’t affected much by fasting. Your doctor will provide specific instructions when ordering your test. Follow their recommendations to ensure accurate results.
Can I test my HGH levels at home?
No. There are no legitimate home HGH or IGF-1 tests. You must have blood drawn at a lab and the sample analyzed by a certified laboratory. Some companies sell “home hormone tests,” but these aren’t reliable for diagnosing growth hormone deficiency. Proper testing requires a lab-certified blood draw and analysis by a medical laboratory.
What time of day should HGH be tested?
For direct HGH testing (which is rarely used), the time of day matters because GH levels fluctuate throughout the day. However, IGF-1 (which is what your doctor actually tests) is stable throughout the day, so timing doesn’t matter for IGF-1 testing. Your doctor will provide specific instructions. Generally, fasting blood draws are done in the morning, but this is more for consistency than for HGH specifically.
Medical Disclaimer: The information on this page is for educational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, stopping, or changing any hormone therapy or medication. Individual results vary, and treatment decisions should be made between you and your doctor based on your specific medical history and needs.
National HRT Staff
Please note that the information provided in this article is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.