Growth hormone test: normal range and results (GH)
Also known as: STH
- Updated
- 2026-09-30
- Every number with its source
What growth hormone is
Growth hormone (somatotropin, abbreviated STH or GH) is produced in the pituitary gland — a gland at the base of the brain. It stimulates the growth and division of cells, affects the development of bones and muscles in childhood and adolescence, and in adults takes part in metabolism — the breakdown of fat and the metabolism of glucose and protein. The release of growth hormone is not constant: it pulses through the day and most of it is released during sleep, so a single random measurement is not always informative. Stimulation or suppression tests are sometimes needed, in which a doctor takes several samples over a period of time after giving a medicine or glucose. The amount of growth hormone is also reflected indirectly by another marker — IGF-1 (insulin-like growth factor 1), which is more stable in the blood and is often tested together with, or instead of, a one-off GH measurement.
Reference ranges
| Group | Range, µg/l | Source | |
|---|---|---|---|
| Adult men 0.05–3 ng/ml per MedlinePlus; 1 ng/ml = 1 µg/l | 0.05–3 | MedlinePlus Reviewed 2026-01-25 | |
| Adult women 0.05–8 ng/ml per MedlinePlus; 1 ng/ml = 1 µg/l | 0.05–8 | MedlinePlus Reviewed 2026-01-25 | |
According to the MedlinePlus source, the normal blood level of growth hormone for adult men is 0.05–3 µg/l (ng/ml) — a narrower and lower interval than for adult women, who are given 0.05–8 µg/l. The source notes that growth hormone is released in pulses and that the size and duration of the pulses change with the time of day, age and sex — this is the only circumstance MedlinePlus links to the fact that the intervals for men and women are presented separately. It gives no more precise biological explanation for why the upper limit for men in particular is lower. In children the interval depends on age, so it is stated by the doctor. A specific result should above all be compared with the range that the laboratory which performed the test gives in its own report, because the limits can differ slightly between laboratories.
For adult women the same source gives 0.05–8 µg/l (ng/ml) — a wider and higher interval than for adult men, who are given 0.05–3 µg/l. Here too the source states that growth hormone is released in pulses and that the size and duration of the pulses vary with the time of day, age and sex — that is what MedlinePlus mentions as the circumstance connected with publishing separate intervals for men and women. It does not explain the specific physiological reason why the upper limit for women is higher. In children the norm depends on age and sex, and for pregnancy the source gives no separate interval. When interpreting a result, what matters most is to compare it with the range stated by the laboratory that carried out the test, because the limits can differ slightly between laboratories.
When the test is ordered
- In children, when the rate of growth lags behind that of peers, or when height, the length of the arms and legs, and weight are lower than expected for age and sex
- In children, when puberty is delayed or the genitals appear small in boys
- In adults, when signs typical of acromegaly appear — a deepened voice, enlarged facial features (lips, nose, tongue), increased sweating, thickened bones, oily and coarse skin
- In children, when signs typical of gigantism appear — rapid growth, a disproportionately large head, large hands and feet, obesity
- When a pituitary tumour or another disorder of pituitary function is suspected
- To monitor the course of treatment of an already diagnosed growth hormone disorder
How to prepare
- A doctor may give specific instructions on what you may or may not eat and drink before the test — sometimes you need to go without food for a few hours
- Because the amount of growth hormone in the blood varies through the day, a doctor may order several samples or a stimulation/suppression test rather than a single blood draw
A raised growth hormone result
A raised growth hormone level in adults is most often linked to acromegaly and in children to gigantism; both are most often caused by a pituitary tumour or a disorder of the cells that produce the hormone. It is assessed together with IGF-1 and imaging tests of the pituitary gland.
Causes of a raised result
- A pituitary tumour producing too much growth hormone
- Acromegaly in adults — a slowly progressing condition caused by a long-term excess of growth hormone
- Gigantism in children, when the bone growth plates have not yet closed
- Resistance to growth hormone (the body cannot use it properly, so its production rises to compensate)
Signs of excess growth hormone
- A deepened, hoarse voice
- Enlarged facial features — lips, nose, tongue
- Hands and feet larger than usual
- Thickened bones
- Coarse, oily skin, increased sweating and body odour
- An irregular menstrual cycle in women, erectile problems in men
- In children — rapid growth, a disproportionately large head, mild or moderate obesity
What is usually assessed after a raised result
- The IGF-1 marker — it is more stable through the day and is often used to confirm an excess of growth hormone
- An imaging test of the pituitary gland (MRI), if a tumour is suspected
- A suppression test (glucose suppression test), which a doctor may order for more precise diagnosis
- A consultation with an endocrinologist about further care
A low growth hormone result
A low growth hormone level in children is linked to slowed growth and in adults to pituitary insufficiency (hypopituitarism). In adults this test is done less often, because the symptoms tend to be vague.
Causes of a low result
- Pituitary insufficiency (hypopituitarism) — impaired function of the pituitary gland
- A congenital or acquired growth hormone deficiency in childhood
- Damage to the pituitary gland after a tumour, surgery or radiotherapy
Signs of a growth hormone deficiency
- In children — a slowed rate of growth compared with children of the same sex and age
- In children — shorter height, shorter arms and legs, lower weight
- In children — small genitals in boys, delayed puberty
- In adults — tiredness, reduced bone density and reduced muscle mass
What is usually assessed after a low result
- The IGF-1 marker for additional confirmation
- A stimulation test, in which a doctor gives a medicine or glucose and follows how GH changes over time
- An imaging test of the pituitary gland, if structural damage is suspected
- In children — following the growth chart and a consultation with an endocrinologist
Related pages
IGF-1 is more stable in the blood and is often tested together with, or instead of, a one-off growth hormone measurement. Other tests explained in English on this site: TSH and prolactin. See also how to read blood test results and how to prepare for a blood test.
Full site in Lithuanian: proactiva.app
Frequently asked questions
›What is the normal growth hormone range in blood?
According to MedlinePlus, the range for adult men is 0.05–3 ng/ml (µg/l) and for adult women 0.05–8 ng/ml. In children the norm depends on age and sex. Because the amount of the hormone varies through the day, the exact interval and the interpretation are given by the laboratory and the doctor.
›Why does the growth hormone level in blood vary?
Growth hormone is released in pulses, mostly during deep sleep, so a one-off measurement during the day may not reflect the true situation. That is why a doctor sometimes orders several samples or a stimulation or suppression test.
›How do the growth hormone and IGF-1 tests differ?
Growth hormone (GH) in the blood varies through the day, while IGF-1 (insulin-like growth factor 1), whose production is stimulated by GH, is more stable and is often used as a more reliable long-term indicator of growth hormone status.
›Which signs suggest a raised growth hormone in adults?
According to MedlinePlus, the signs typical of acromegaly are a deepened voice, enlarged facial features, larger hands and feet, thickened bones, coarse oily skin and increased sweating. These signs are worth discussing with a doctor.
›Which signs suggest a low growth hormone in children?
According to MedlinePlus, these are a slowed rate of growth compared with peers, lower height, shorter arms and legs and lower weight, and sometimes delayed puberty. If you notice such signs, it is worth seeing a doctor.
›Is any special preparation needed before a growth hormone test?
According to MedlinePlus, a doctor may give specific instructions about eating and drinking before the test, and in some cases asks you to go without food for a few hours. The specific instructions are always given by the doctor who orders the test.
›What are the limits for the growth hormone suppression (glucose) test?
For a suppression test, blood is taken fasting in the morning, a glucose solution is then drunk, and samples are taken for another 1–2 hours. According to MedlinePlus, growth hormone normally falls below 1 ng/ml after the glucose; if it stays raised and does not fall, acromegaly in adults or gigantism in children is suspected. Laboratory limits may differ slightly.
›What are the limits for the growth hormone stimulation test?
For a stimulation test, a medicine that triggers growth hormone release is given into a vein and blood is taken several times over 2–5 hours. According to MedlinePlus, a peak value of 10 ng/ml (10 µg/l) or more is considered normal and rules out growth hormone deficiency, 5–10 ng/ml is indeterminate, and 5 ng/ml or less is subnormal. A subnormal response is linked to growth hormone deficiency in children and to adult growth hormone deficiency in adults.
Sources
- MedlinePlus (US National Library of Medicine): Growth Hormone Test — 2026-09-06
- MedlinePlus: Growth Hormone Tests — 2026-09-06
- MedlinePlus: Growth hormone suppression test — 2026-09-29
- MedlinePlus: Growth hormone stimulation test — 2026-09-29
Related markers
This site is not an emergency service. If severe chest or head pain, breathlessness, confusion, difficulty speaking, heavy bleeding or another acute problem has come on suddenly — do not wait for tests, call 112.
This information is not a diagnosis and does not replace a consultation with a doctor. Reference ranges depend on the laboratory, your age and sex — always compare your result with the range printed on your own report.