The essentials

A growth hormone (GH) test measures a pituitary hormone that drives growth in children and helps control muscle, fat and bone in adults. Because GH is released in short pulses, a single random value says little: doctors rely on IGF-1 and on dynamic tests. A stimulation test looks for too little GH; a glucose suppression test looks for too much (acromegaly).

How do I read a growth hormone result on my report?

Fictitious example of a growth hormone stimulation test report (United States format)
TestResultReference / cut-offFlag
Growth hormone, baseline (0 min)0.3 ng/mL0.0-10.0 ng/mL
Growth hormone, 30 min1.8 ng/mLsee peak
Growth hormone, 60 min2.6 ng/mLsee peak
Growth hormone, peak2.6 ng/mLpeak above 5 ng/mL expectedL
IGF-1 (somatomedin C)62 ng/mLage-specific range: 83-233 ng/mLL
  1. Baseline value: a low GH at rest is normal, because GH is released in pulses and its half-life is only 20 to 25 minutes[2].
  2. Timed samples: after a stimulating medicine, GH should rise. The highest value, the peak, is the number that counts[1].
  3. Cut-off: it depends on the test used, the person's age and weight; it is not a "normal range" in the usual sense[5].
  4. IGF-1: made by the liver under the effect of GH, it is stable through the day and is read against age-specific values. The ranges shown here are invented for the example; your laboratory's figures are the ones that count.

A stimulation test, IGF-1 and other hormones on the same report can be hard to follow. BloodSense explains each line of your complete report in plain words and helps you prepare your questions for the endocrinologist.

Explain my hormone results

What is a growth hormone test used for?

Growth hormone, also called somatotropin or human growth hormone (HGH), is made by the pituitary gland at the base of the brain. GH tests are used to find and follow growth hormone deficiency, gigantism and acromegaly, and to check the pituitary gland[1].

  • In children: slow growth, short stature compared with peers, delayed puberty; or, rarely, excessive growth with large hands and feet[1].
  • In adults: after pituitary surgery, a pituitary tumor, head injury or radiotherapy, when tiredness, lower muscle mass or weaker bones suggest a deficiency[1][5]; or when the face, hands and feet slowly enlarge, suggesting acromegaly[1].

There are three ways of measuring it[1][2]:

  • Random GH: a single fasting sample. Useful in a few situations, but of limited value on its own.
  • Stimulation test: a medicine is given to make the pituitary release GH, and blood is drawn several times over about two hours. It looks for a deficiency.
  • Suppression test: you drink a glucose solution, and blood is drawn every 30 minutes for two hours. In a healthy person, sugar switches GH off. It looks for an excess.

The IGF-1 blood test is usually done first or alongside, because it reflects average GH activity. IGFBP-3, its carrier protein, is sometimes added in children[1].

What are normal growth hormone levels?

There is no single normal value: the meaning depends on the test. Results are given in ng/mL, which is the same as µg/L.

Usual growth hormone thresholds by test (your laboratory and doctor may use different cut-offs)
TestResult that is reassuringResult that suggests a problemSource
Random fasting GH (adult)0.0-10.0 ng/mL (reference interval of one large US laboratory)Not diagnostic aloneLabcorp[2]
Stimulation test, childPeak at or above 10 ng/mL (traditional cut-off)Peak below 10 ng/mL, interpreted with growth dataPediatric Endocrine Society[3]
Insulin tolerance test, adultPeak above 5 ng/mLPeak 5 ng/mL or lessAACE[5]
Glucagon test, adultPeak above 3 ng/mL (normal weight) or above 1 ng/mL (obesity)At or below these valuesAACE[5]
Macimorelin oral test, adultPeak above 2.8 ng/mLPeak 2.8 ng/mL or lessGarcia et al.[6]
Glucose suppression test (OGTT)Lowest GH below 1 ng/mLGH stays at 1 ng/mL or moreEndocrine Society[7]

Your laboratory's reference values and your doctor's interpretation take precedence: GH assays differ, and recent guidelines stress caution when comparing results from different methods[5].

What does high or low growth hormone mean?

Low GH response (possible deficiency)

  • Common False low result: obesity blunts the GH response, so cut-offs are lower in people with a high body weight[5]. Before puberty, a low peak is also common in children who will turn out to be normal; for this reason the guideline suggests sex-steroid "priming" before testing in prepubertal boys over 11 and girls over 10[3].
  • Common Other causes of slow growth: low thyroid hormone (TSH, FT4 (thyroxine)), poor nutrition or chronic illness lower IGF-1 and growth without true GH deficiency.
  • Possible Pituitary damage in adults: a tumor, surgery, radiotherapy or head injury. An adult with three or more other pituitary hormones missing and a low IGF-1 is so likely to be GH deficient that a stimulation test may not be needed[4].
  • Rare Congenital or genetic GH deficiency in children, or resistance to GH (high GH with low IGF-1).

GH that does not fall (possible excess)

  • Common Stress, exercise, sleep and fasting raise GH for a short time; poorly controlled diabetes, liver or kidney disease can also raise it.
  • Rare Acromegaly in adults or gigantism in children, almost always caused by a benign pituitary tumor[1]. In a person with typical features, an IGF-1 above 1.3 times the upper limit for age confirms acromegaly; a random GH is not required for the diagnosis[8].

How do I prepare for a growth hormone blood test?

  • Fast as instructed: random GH is drawn on an empty stomach, after resting for at least 30 minutes[2].
  • Avoid hard exercise before the test: physical effort raises GH.
  • Tell the team about all your medicines, especially estrogen or birth-control pills, steroids, insulin and diabetes medicines.
  • For a stimulation or suppression test, plan about two to three hours on site, with a small tube left in a vein[1].
  • For an insulin tolerance test, expect to be watched closely: it lowers blood sugar on purpose and is not suitable for everyone[5].
  • Bring your child's growth chart and earlier height measurements if the test is for a child.

When should I see a doctor about growth hormone?

When to see a doctor

  • Emergency: call 911 if, during or after a stimulation test, you or your child has confusion, sweating with shaking that does not improve with sugar, a seizure or fainting, or if a pituitary tumor causes a sudden severe headache with vision loss.
  • Within 24 to 48 hours if a known pituitary problem comes with new, marked tiredness, vomiting or dizziness, which may mean other pituitary hormones are failing.
  • At your next appointment to discuss a child who grows more slowly than peers, an adult with changing facial features or larger hands and feet, or any abnormal GH or IGF-1 result.

Questions to ask your doctor

  1. Which test was used, and which cut-off applies to my age and weight?
  2. Is my IGF-1 in line with the GH result?
  3. Do other pituitary hormones need checking (thyroid, cortisol, sex hormones)?
  4. Should the test be repeated, or confirmed with a second stimulation test?
  5. Is an MRI of the pituitary gland needed?

Frequently asked questions

Can I test my growth hormone with a single blood draw?

Only in part. A single GH value changes from minute to minute. IGF-1 gives a better picture of average GH activity, and dynamic tests are needed to confirm a deficiency or an excess[2].

What is the difference between GH and IGF-1?

GH is the pituitary signal; IGF-1 is the liver's answer to that signal. GH swings through the day, while IGF-1 stays fairly stable, so it is used for screening and follow-up.

Does GH fall with age?

Yes, GH secretion and IGF-1 decrease naturally with age, which is why IGF-1 is read against age-specific values. A lower level in an older adult is expected and is not a reason, by itself, for treatment.

Can sport or supplements change the result?

Hard exercise and sleep raise GH briefly. Injected GH taken outside medical care can raise both GH and IGF-1, and it is banned in sport; tell your doctor about any hormone products you use.

  1. MedlinePlus. Growth hormone tests. Updated September 24, 2024. US National Library of Medicine. medlineplus.gov (accessed October 27, 2026)
  2. Labcorp. Growth hormone (test 004275): limitations, reference interval and patient preparation. labcorp.com (accessed October 27, 2026)
  3. Grimberg A, DiVall SA, Polychronakos C, et al. Guidelines for growth hormone and insulin-like growth factor-I treatment in children and adolescents: growth hormone deficiency, idiopathic short stature, and primary insulin-like growth factor-I deficiency. Horm Res Paediatr. 2016;86(6):361-397. doi:10.1159/000452150 (accessed October 27, 2026)
  4. Molitch ME, Clemmons DR, Malozowski S, et al. Evaluation and treatment of adult growth hormone deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(6):1587-1609. doi:10.1210/jc.2011-0179 (accessed October 27, 2026)
  5. Yuen KCJ, Biller BMK, Radovick S, et al. American Association of Clinical Endocrinologists and American College of Endocrinology guidelines for management of growth hormone deficiency in adults and patients transitioning from pediatric to adult care. Endocr Pract. 2019;25(11):1191-1232. doi:10.4158/GL-2019-0405 (accessed October 27, 2026)
  6. Garcia JM, Biller BMK, Korbonits M, et al. Macimorelin as a diagnostic test for adult GH deficiency. J Clin Endocrinol Metab. 2018;103(8):3083-3093. doi:10.1210/jc.2018-00665 (accessed October 27, 2026)
  7. Katznelson L, Laws ER Jr, Melmed S, et al. Acromegaly: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2014;99(11):3933-3951. doi:10.1210/jc.2014-2700 (accessed October 27, 2026)
  8. Giustina A, Biermasz N, Casanueva FF, et al. Consensus on criteria for acromegaly diagnosis and remission. Pituitary. 2024;27(1):7-22. doi:10.1007/s11102-023-01360-1 (accessed October 27, 2026)

This page is general information. It does not replace the advice of a doctor, who interprets growth hormone tests with growth data, other hormones, imaging and examination.