What is IGF-1 on a blood test?
IGF-1 is a hormone your liver makes in response to growth hormone.
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The short answer
IGF-1 is a hormone your liver makes in response to growth hormone. Because growth hormone is released in pulses and disappears within minutes, IGF-1 is measured instead: it's stable through the day and reflects growth hormone activity over time. At Epicentre it's R794, walk-in, no doctor's referral. Special collection, so confirm with the branch when you book.
What does IGF-1 measure?
Growth hormone comes out of the pituitary in bursts, mostly at night, and clears from the blood within minutes. Measuring it directly tells you almost nothing unless you catch a pulse. So your liver's response to it is measured instead.
IGF-1 does the work growth hormone is credited with: it tells muscle, bone and other tissue to grow and repair. It stays steady through the day, which makes it the practical way to assess growth hormone status.
It also declines steadily with age, which is why it turns up in longevity work, and why the reference range that applies to you depends heavily on how old you are.
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Ask us on WhatsAppSee all 102 markersWhat does a high or low IGF-1 mean?
Before reading much into either, remember how reference ranges work. They are built so that about 95% of healthy people fall inside them, so roughly 1 in 20 normal results sits outside by definition. The pattern across related markers matters far more than any single value.
What else affects IGF-1?
- Your age
- This is the big one. IGF-1 falls throughout adult life, so a result is only meaningful against an age-matched range. A value that is fine at 55 would be low at 25.
- Nutrition
- IGF-1 drops with under-eating and prolonged calorie restriction, independently of anything hormonal. Fasting protocols lower it.
- Liver function
- Your liver makes it, so liver disease lowers IGF-1 even when growth hormone output is normal.
- Thyroid status
- Untreated hypothyroidism suppresses it, which is one reason thyroid markers are read alongside.
The functional view
IGF-1 is the clearest example of a marker where both ends of the range matter, and where the functional reading is genuinely two-directional.
Low IGF-1 is associated with poor recovery, low muscle mass and reduced bone density. High IGF-1 is associated in population studies with increased risk of some cancers. The interesting position is not 'as high as possible', which is how it's sometimes discussed in performance circles, but somewhere sensible for your age.
That makes the age-matched range the whole game. A single number means nothing without knowing how old the person is, which is why the functional report prints the range that applies to you rather than a universal one.
Where this marker sits in the bigger picture
Energy
How your body builds, repairs and fuels itself. IGF-1 is one of the main signals telling tissue to grow.
Every blood order at Epicentre comes back with a functional health report at no extra cost, showing each marker against an optimal band as well as the standard range, ranked by what needs attention. Functional optimal ranges are educational reference recommendations rather than diagnostic thresholds, they are not universally agreed, and a value inside a standard laboratory range is not a disease. The standard report is still the one your doctor works from.
Which markers is it read with?
TSH R237 and free T4 R237, since thyroid status affects it. Liver function tests R522, because your liver produces it. And if the question is body composition or performance, testosterone R221 and HbA1c R280.
Which packages include IGF-1?
None of our standard packages carry IGF-1, so it is ordered on its own or added to another panel. Tick it on the interactive cash pricelist alongside whatever else you need, or message the branch and they will build the order with you.
Want it added to a panel? Tell us what else you are testing and we will price it together.
Ask us on WhatsAppBuild your own on the pricelistWhere can I test IGF-1 in South Africa?
All three open Monday to Friday, 08:30 to 16:00, closed on public holidays. Medical aid rates are roughly 20% higher than the cash rate and generally need a doctor's request with an ICD-10 code.
Basically
IGF-1 is R794 at Epicentre and you do not need a referral for it. It is a functional marker, which means a standard panel will not include it unless you ask. One result on its own rarely settles anything: what matters is the pattern with the markers it is read alongside, and what it has done since last time.
Frequently asked questions
What is a normal IGF-1 level?
There isn't one number, because IGF-1 falls steadily throughout adult life. Your result prints against an age-matched reference range, and a value that's perfectly normal at 55 would be low at 25. That's why the age on the request form matters more for this marker than for most.
Does IGF-1 measure growth hormone?
Indirectly, and that's the point. Growth hormone is released in pulses, mostly at night, and clears within minutes, so a single measurement of it is close to meaningless. IGF-1 is what your liver makes in response, it stays stable through the day, and it reflects growth hormone activity over a period rather than at an instant.
Can I raise my IGF-1 naturally?
Adequate protein, resistance training and proper sleep all support it, and chronic under-eating lowers it. But higher is not automatically better: population studies associate persistently high IGF-1 with increased risk of some cancers, so this is a marker to discuss with a clinician rather than to optimise on your own.
Why does IGF-1 need special collection?
The sample needs particular handling, so it's marked as a special collection on our pricelist. Phone the branch before you come in and they'll confirm what's needed. It doesn't change the price, it just means the branch needs to be expecting you.
Other markers explained
This page is general health information and not a medical diagnosis. Epicentre Aids Risk Management (Pty) Ltd, practice number 1117394, provides diagnostic laboratory testing: we do not diagnose, prescribe or treat, and results are intended to inform a consultation with your doctor. Medically reviewed by Dr Samantha Naidoo, MB ChB, FCP (SA), Medical Director. Prices are 2026 cash rates including 15% VAT and can change without notice.