Quick answer: An IGF-1 test is a blood test that measures insulin-like growth factor 1, a hormone produced mainly by the liver in response to growth hormone (GH) signaling. Because IGF-1 stays stable in the blood for hours while GH itself spikes and crashes throughout the day, IGF-1 is the standard clinical proxy for overall GH activity. Doctors order it to investigate short stature in children, suspected acromegaly or GH deficiency in adults, and increasingly as a longevity biomarker since both very low and very high IGF-1 levels are linked to worse health outcomes.
What does an IGF-1 test actually measure?
The IGF-1 test quantifies the concentration of insulin-like growth factor 1 in your serum, reported in nanograms per milliliter (ng/mL). IGF-1 is not the same as growth hormone. GH is released in pulses from the pituitary gland, mostly at night, and its half-life in the bloodstream is less than 30 minutes. By the time most people get a morning blood draw, GH has already cycled through several peaks and troughs, making a single GH measurement close to useless for screening purposes. IGF-1 solves that problem: the liver converts GH signals into a steady IGF-1 output that persists for 12 to 20 hours, giving a reliable 24-hour average of GH activity.
About 80 percent of circulating IGF-1 travels bound to a carrier protein called IGFBP-3. Some panels measure both markers together for a more complete picture of the GH axis, but a standalone IGF-1 is sufficient for most clinical questions. The test requires a standard venous blood draw and no fasting, though severe caloric restriction and acute illness can transiently suppress IGF-1 independent of GH status, a detail worth noting before you interpret a borderline-low result.
IGF-1 normal range: what numbers actually mean by age and sex
The simplest way to actually get this done
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IGF-1 declines sharply with age, so a result that looks low in a 70-year-old would be considered elevated in a 20-year-old. Reference ranges vary slightly by laboratory and assay method, but the table below reflects typical Labcorp and Quest consensus values for adults.
| Age range | Male reference range (ng/mL) | Female reference range (ng/mL) |
|---|---|---|
| 20 to 24 | 182 to 780 | 182 to 780 |
| 25 to 29 | 114 to 492 | 114 to 492 |
| 30 to 39 | 90 to 360 | 90 to 360 |
| 40 to 49 | 71 to 290 | 71 to 290 |
| 50 to 59 | 58 to 240 | 58 to 240 |
| 60 to 69 | 48 to 185 | 48 to 185 |
| 70 and older | 38 to 160 | 38 to 160 |
Children and adolescents have markedly higher IGF-1 during the pubertal growth surge, often reaching 300 to 900 ng/mL at peak puberty, which is why pediatric endocrinologists use separate age- and sex-specific charts. If your lab report comes back with a flag, check that the reference range printed on the report matches your age bracket. Laboratories set their own internal normals, and a flag at one lab may not be a flag at another.
How to read your own IGF-1 as a percentile, not just a pass or fail
The most useful way to interpret an IGF-1 result is to locate it inside your age band rather than to ask only whether it is flagged. A 45-year-old with an IGF-1 of 90 ng/mL and one of 270 ng/mL are both technically “normal,” yet they sit at opposite ends of the same range and tell very different stories about GH drive, nutrition, and long-term risk. Ask yourself where in the band your number falls: bottom third, middle, or top third. That placement, tracked over time on the same assay, carries more signal than a single in-range or out-of-range label. It is also why a value that has drifted from the 60th percentile toward the 20th over a few years deserves attention even if it never crosses a flag, and why a stable mid-range number in a symptom-free adult is usually reassuring rather than something to optimize.
Why IGF-1 and growth hormone are tested together
The IGF-1 test is almost always the first-line screen for GH axis disorders, and GH stimulation or suppression tests are reserved for confirmation. Here is why that workflow exists. In acromegaly, the pituitary secretes excess GH continuously. A single random GH measurement might catch a pulse and look high, but it also might catch a trough and look normal. IGF-1 averages out those fluctuations: in untreated acromegaly, IGF-1 is reliably elevated above the age-adjusted upper limit. Conversely, in adult GH deficiency, IGF-1 is persistently low even though GH pulsatility might look superficially intact on a random draw.
The clinical sequence in endocrinology practice typically runs: (1) IGF-1 screening, (2) if borderline, add IGFBP-3, (3) if still unclear, proceed to a GH stimulation test (insulin tolerance test or glucagon stimulation test) in a supervised clinical setting. That third step carries real risk and is not done outside a specialty clinic. So when a clinician orders just an IGF-1 blood test initially, that is deliberate protocol, not laziness. For anyone curious about their best biomarkers to test for a longevity baseline, IGF-1 sits near the top of the list precisely because it opens the door to further endocrine evaluation if needed.
What causes high IGF-1?
The most medically significant cause of persistently high IGF-1 is a GH-secreting pituitary adenoma, the underlying mechanism of acromegaly. In adults, acromegaly presents gradually: jaw widening, hand and foot enlargement, carpal tunnel syndrome, increased sweating, and eventually cardiovascular complications. IGF-1 above the age-adjusted upper limit on two separate draws, combined with a non-suppressible GH during an oral glucose tolerance test, confirms the diagnosis. Treatment is surgical (transsphenoidal resection) or medical (somatostatin analogs).
Outside acromegaly, these factors commonly push IGF-1 upward:
- Puberty and pregnancy: physiological elevations, not pathological.
- Exogenous GH use: prescription GH replacement at supraphysiologic doses, or illicit GH use in athletes, reliably raises IGF-1.
- High protein and caloric surplus: nutritional status is one of the strongest modulators of IGF-1 outside the GH axis. A high-protein diet (1.8 g/kg or more) combined with a caloric surplus can raise IGF-1 by 15 to 25 percent compared to a deficit state.
- Insulin resistance and obesity: paradoxically, obesity typically lowers IGF-1 despite high insulin because GH secretion is suppressed; however, some insulin-resistant individuals show elevated free IGF-1 due to reduced IGFBP-3.
- Hyperthyroidism: accelerated GH pulsatility can modestly raise IGF-1.
The longevity dimension here is nuanced. Several large prospective cohorts, including follow-up studies from the UK Biobank, have reported that men with IGF-1 in the top quartile face modestly higher cancer risk (particularly colorectal and prostate). That association is not a diagnosis and does not indicate you need treatment, but it is a reason to track the number over time rather than ignore a single high result.
What does low IGF-1 mean?
Low IGF-1 relative to your age-adjusted reference range can signal GH deficiency, but it is more often explained by non-endocrine factors. The liver synthesizes most circulating IGF-1, so any condition that impairs liver function, including cirrhosis, hepatitis, and severe malnutrition, will depress IGF-1 even when the GH axis is functioning normally. The same is true for poorly controlled type 1 diabetes and hypothyroidism.
In adults, genuine GH deficiency usually results from pituitary damage: prior radiation, surgery, tumor mass effect, or traumatic brain injury. These patients typically present with fatigue, reduced lean mass, increased central adiposity, and metabolic abnormalities. IGF-1 below the lower reference limit in that clinical context warrants a formal stimulation test, not just reassurance.
From a longevity standpoint, low IGF-1 tells a different story in older adults. Caloric restriction research in model organisms consistently shows that suppressing the GH/IGF-1 axis extends lifespan, and some centenarian cohort studies have found that the oldest-old cluster in the lower half of the normal range. The practical implication: a 68-year-old with an IGF-1 of 55 ng/mL who feels well and has no muscle wasting is probably not GH-deficient; they may simply be showing the expected age-related decline. Context is everything, which is why the albumin test and other nutritional markers belong in the same draw to rule out protein-energy malnutrition before attributing low IGF-1 to the GH axis alone.
IGF-1 and aging: the U-shaped curve you need to understand
The relationship between IGF-1 and longevity is not linear, and that is the single most important thing most people miss when they Google this test. Very low IGF-1 in middle-aged adults predicts frailty, sarcopenia, and cardiovascular events. Very high IGF-1 is associated with certain cancers and, in some studies, overall mortality. The sweet spot appears to be the middle of the age-adjusted range, roughly the 40th to 60th percentile for your decade, though no randomized trial has proven that titrating IGF-1 into that zone extends life.
The mechanism behind the cancer signal involves IGF-1 acting as a mitogenic signal: it promotes cell proliferation and inhibits apoptosis through the PI3K/Akt/mTOR pathway. Elevated IGF-1 may accelerate the growth of already-initiated tumor cells rather than directly cause cancer. This is why rapamycin researchers, who are interested in mTOR inhibition as an anti-aging intervention, pay close attention to IGF-1 as a pathway readout.
On the other side of the U, the sarcopenia risk from chronically low IGF-1 is well documented. Muscle protein synthesis depends partly on IGF-1 signaling. Adults over 60 who lose lean mass rapidly and show low-normal or below-range IGF-1 are candidates for endocrine evaluation and, sometimes, supervised GH replacement if a true deficiency is confirmed. Connecting IGF-1 to other age-related metabolic markers like adiponectin gives a more complete metabolic picture than either marker alone.
A short scenario ties the U-shape to a real decision. A 52-year-old man reads that higher IGF-1 builds muscle and asks his clinician about GH. His IGF-1 comes back at 210 ng/mL, comfortably mid-range for his age, and his body composition is fine. Pushing that number higher with exogenous GH would move him toward the cancer-associated end of the curve for no proven benefit, so the right answer is to leave it alone and track it. Contrast that with a 74-year-old woman losing grip strength and weight, whose IGF-1 sits at 40 ng/mL with low albumin. Here the number is a prompt to rule out malnutrition first, then consider a formal endocrine workup if the nutritional picture is clean. Same test, opposite conclusions, and neither is settled by the raw number in isolation.
IGF-1 test cost: what to expect in 2026
Cash-pay pricing varies considerably depending on the order route. The test itself is a straightforward immunoassay run on automated platforms, so the laboratory cost is not particularly high; the price you see reflects markup through various ordering channels.
| Order route | Typical 2026 cash price | Notes |
|---|---|---|
| Direct-to-consumer lab (e.g., Ulta Lab Tests, Walk-In Lab) | $45 to $85 | Draw at Quest or Labcorp PSC; results in 1 to 3 business days |
| Physician-ordered at Quest or Labcorp | $80 to $200 before negotiated rates | Insurance typically covers with appropriate diagnosis code (E22.0, E23.0) |
| Comprehensive longevity panel (includes IGF-1) | $249 to $599 | Often the most cost-effective per-marker route |
| Urgent care or urgent-order clinic | $150 to $350 | Higher overhead; use only if speed is critical |
| Medicare Part B | $0 co-pay if medically necessary | Covered under diagnosis of suspected GH disorder; not covered as wellness screening |
HSA and FSA funds cover IGF-1 testing when ordered by a clinician with a documented clinical indication. For self-pay wellness testing without a physician order, HSA/FSA eligibility depends on whether you have a Letter of Medical Necessity from your provider. Most direct-to-consumer labs do not automatically supply one, so ask before ordering if you plan to use pre-tax dollars.
If you are getting blood drawn anyway for a routine complete blood panel, bundling an IGF-1 add-on is almost always cheaper per marker than ordering it standalone later. Most direct-to-consumer platforms allow menu-style add-ons at the checkout step with a single venipuncture.
If you are getting blood drawn anyway, it is often smarter to capture a full baseline at once. Here is how a full-body panel compares in terms of markers covered and per-draw value.
How to prepare for an IGF-1 test and what happens at the draw
No fasting is required, but a few factors can affect your result and are worth knowing about before you walk into the phlebotomy room. Intense exercise in the 24 hours before the draw can transiently elevate GH and therefore IGF-1, though the effect is usually modest. More important: if you are acutely ill, have not eaten adequately for several days, or are in the middle of a very-low-calorie diet phase, your IGF-1 may read artificially low. Most endocrinologists recommend testing during a period of dietary normalcy, meaning at least 3 to 5 days of regular food intake.
The draw itself is a single tube of blood, typically a red-top or gold-top SST tube. No special handling beyond standard refrigeration is needed. Results at major reference labs return in 24 to 72 hours. Some direct-to-consumer platforms show a preliminary result in 24 hours with a final confirmed result at 48 hours; the two rarely differ.
For serial monitoring (tracking IGF-1 over months or years), use the same laboratory platform each time. Assay methods differ between labs: a Roche Cobalt immunoassay at Quest and a Diasorin Liaison assay at another lab can return numerically different results from the same blood sample. Swapping labs mid-course makes trend analysis unreliable. Talk to a clinician about interpreting your trend results in context of your age, symptoms, and any medications that affect the GH axis.
If a result comes back abnormal, resist the urge to act on it immediately. A low value in someone who was dieting hard, ill, or under-eating in the days before the draw should be repeated after 3 to 5 days of normal food intake before it is taken seriously, and a high value should be confirmed on a second draw before any acromegaly workup proceeds. When you are tracking a deliberate change, whether that is more protein, a fasting protocol, or a medication that touches the GH axis, allow at least 8 to 12 weeks before retesting, because IGF-1 reflects an integrated signal that shifts over weeks rather than days. Retesting too soon mostly measures noise.
What people get wrong about the IGF-1 test
Three misconceptions come up repeatedly in functional medicine and longevity circles, and they are worth correcting directly.
Misconception 1: A single low result proves GH deficiency. It does not. Low IGF-1 is a screening flag, not a diagnosis. Malnutrition, liver disease, hypothyroidism, and even a stressful week before the draw can all suppress IGF-1 without any pituitary problem. The diagnosis of adult GH deficiency requires a stimulation test and a clinical history of pituitary damage or prior deficiency onset. Self-diagnosing based on a wellness IGF-1 panel and then sourcing GH online is dangerous and illegal.
Misconception 2: Higher IGF-1 always means better muscle and healthier aging. This is a popular idea in bodybuilding communities, but the epidemiology does not support uncritical optimization upward. The cancer promotion signal at high IGF-1 is modest but real, especially for prostate and colorectal cancer in men. Middle-of-range, not maximum, is the better target framing.
Misconception 3: IGF-1 testing is equivalent to a growth hormone test. They measure different things. A random GH level without clinical context is nearly uninterpretable given pulsatile secretion. IGF-1 is the practical surrogate for integrated GH activity. Ordering both in a wellness setting adds cost without meaningful additional information unless you are already in an endocrinology workup.
For a broader view of how IGF-1 fits alongside other metabolic and aging markers, the alkaline phosphatase test is another liver-linked biomarker that rounds out the picture when nutritional or hepatic suppression is suspected.
FAQ
What is a normal IGF-1 level for a 40-year-old?
For most 40 to 49-year-olds, the reference range at major US labs falls roughly between 71 and 290 ng/mL, with the midpoint around 160 ng/mL. Values in the lower third of that range warrant checking thyroid function and nutritional status before assuming a GH axis problem. Values in the upper third without symptoms generally do not require further workup but are worth tracking annually.
Can IGF-1 levels fluctuate day to day?
Yes, but far less than growth hormone. IGF-1 is relatively stable within a day, with intraday variation of about 10 to 15 percent. Between-day variation over a week of normal living is typically under 20 percent. Significant swings (more than 30 percent) usually reflect a real change in GH drive, nutritional status, or liver function rather than assay noise.
Does diet affect IGF-1 levels?
Meaningfully yes. Protein intake is the strongest dietary driver: multiple controlled feeding studies show that IGF-1 rises with higher protein consumption and falls during protein restriction, independent of total calories. A week of near-zero calorie intake (extended fasting) can drop IGF-1 by 30 to 50 percent. Plant-based diets tend to produce lower IGF-1 than omnivorous diets at matched calorie levels, an association observed in the EPIC-Oxford cohort, though causation is complex.
Is IGF-1 covered by insurance?
When ordered by a physician with a supporting diagnosis code (acromegaly workup, GH deficiency evaluation, short stature in children), IGF-1 is typically covered by commercial insurance and Medicare Part B. Ordered as a wellness or longevity screen without a clinical indication, it is usually denied and billed at cash rates of $45 to $200 depending on the lab and order channel.
Can I order an IGF-1 test without a doctor?
In most US states, yes. Direct-to-consumer lab platforms allow you to order an IGF-1 test online, pay out of pocket, and get your blood drawn at a Quest or Labcorp patient service center without a physician order. Results are released directly to you. Exceptions include New York and New Jersey, which require a licensed provider to authorize all lab tests. Always confirm your state’s rules before ordering.
What medications affect IGF-1?
Several drug classes significantly alter IGF-1 levels. Oral estrogens (but not transdermal estrogen) suppress hepatic IGF-1 production, which is why women on oral contraceptives or oral menopausal hormone therapy often run lower than expected. High-dose corticosteroids suppress GH pulsatility and lower IGF-1. Tamoxifen and other selective estrogen receptor modulators can raise or lower IGF-1 depending on tissue. Exogenous GH and IGF-1 itself (synthetic preparations) obviously raise levels directly. Always list all medications on your lab requisition so your clinician can interpret the result correctly.
Is IGF-1 useful for tracking anti-aging interventions?
It can be, with caveats. IGF-1 is used as a pharmacodynamic marker in rapamycin longevity trials and in GH replacement protocols, so there is precedent for serial monitoring. The limitation is that the target range for optimal longevity has not been established in randomized trials. Most longevity-minded clinicians track IGF-1 annually alongside fasting insulin, IGFBP-3, and body composition data, looking for trend rather than a single absolute number.
What is the difference between IGF-1 and IGF-2?
IGF-2 is another insulin-like growth factor that plays a larger role in fetal development than in adult physiology. It is far less responsive to GH signaling than IGF-1 and is rarely clinically relevant in adults outside of certain rare tumors (particularly non-islet-cell tumor hypoglycemia) and some cancer research contexts. When clinicians say “IGF test” in an adult GH workup, they mean IGF-1.
Should I try to raise or lower my IGF-1?
For most healthy adults with a mid-range result, the honest answer is neither. No randomized trial has shown that nudging IGF-1 up or down within the normal range extends life or prevents disease, and both extremes of the range carry their own risks. The sensible move is to keep the number in view alongside body composition, fasting insulin, and how you actually feel, and to intervene only when there is a clinical reason: confirmed GH deficiency with symptoms on the low end, or a workup for acromegaly on the high end. Chasing a target number for its own sake is exactly the kind of over-optimization the U-shaped curve warns against.
Does exercise change IGF-1?
Yes, in both directions depending on the timeframe. A single hard session, especially resistance or high-intensity training, transiently raises GH and can nudge IGF-1 upward for a day, which is why endocrinologists prefer you avoid intense exercise in the 24 hours before a draw. Over months, regular training supports healthy lean mass and GH signaling without pushing IGF-1 into a risky range in most people. The transient post-workout bump is a reason to standardize your draw conditions, not a lever to game the test.
Can a child’s IGF-1 predict adult height?
Only loosely. In pediatric endocrinology, IGF-1 is one input into evaluating growth, alongside bone age, growth velocity, and the full clinical picture, and it is most useful for flagging GH deficiency or excess rather than forecasting a specific adult height. A single IGF-1 in a growing child is interpreted against tight age- and puberty-stage-specific charts by a specialist, not against adult ranges, and it is never used alone to make a prediction.
