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Blood Test Tracker

IGFBP-3 (IGF Binding Protein 3)

A protein made mostly in the liver that carries IGF-1 in the blood. It rises and falls with growth hormone and with nutrition, and usual levels change a lot with age.

AI-verified against cited sources. Awaiting expert reviewAlso called IGFBP-3, IGFBP3, IGF-BP3LOINC 2483-6

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What it is

IGFBP-3 is the main protein that carries IGF-1 in the blood. IGF-1 is the hormone that growth hormone prompts your liver to make. IGFBP-3 holds on to IGF-1 together with a partner protein, which keeps IGF-1 in the blood longer and controls how much reaches your tissues. IGFBP-3 is made mostly in the liver, and growth hormone helps drive its production. Levels rise through childhood and puberty and then drift down slowly in adult life.

Why it matters

Clinicians use IGFBP-3 together with IGF-1 to look at growth hormone activity. They use it when a child is growing slowly, when adult growth hormone deficiency is a question, and to follow growth hormone treatment. IGF-1 is usually the more useful of the two, and in acromegaly IGFBP-3 adds little (Mayo). IGFBP-3 also falls with poor nutrition and liver disease, so it can reflect more than growth hormone.

If it’s low

A result below your lab's range for your age and sex can mean the body makes less growth hormone, or responds to it less, than usual. More often, low levels reflect poor nutrition, fasting, liver disease or poorly controlled diabetes. Mayo notes that IGFBP-3 and IGF-1 below the 2.5th percentile for age are consistent with growth hormone deficiency or severe resistance, but people with milder problems can still fall within the range.

Common causes

  • Not eating enough calories or protein, fasting, or long-term malnutrition
  • Liver disease
  • Poorly controlled diabetes
  • Older age, since levels drift down slowly in adult life
  • Growth hormone deficiency or resistance (uncommon)

What can help

  • Ask your clinician whether nutrition, liver health or blood sugar control could be affecting this number
  • Ask whether IGF-1 and growth hormone testing makes sense
  • Tell your clinician about any biotin supplement before a repeat test

If it’s high

A result above your lab's range for your age and sex can mean the body is making more growth hormone than usual, or that someone is getting more growth hormone treatment than they need. Chronic kidney failure can also raise it. Assays read quite differently, so a result near the top of the range on one assay can fall within range on another. Clinicians read it with IGF-1, which is usually the better test.

Common causes

  • Puberty and the teen years, when levels are naturally highest (check the range for your age)
  • Differences between assays or labs
  • Chronic kidney failure, because the protein is cleared more slowly
  • Growth hormone treatment that gives more than the body needs
  • A growth hormone-making pituitary tumor (acromegaly or gigantism) (uncommon)

What can help

  • Ask your clinician whether IGF-1 and other pituitary hormones were checked
  • Ask whether kidney function is worth checking
  • Use the same lab for repeat tests so results can be compared

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

The usual range depends on sex and age. Choose women or men to see the one that applies.

Children and teens 36 ranges

See IGFBP-3 by age and sex, with the U.S. survey numbers where they exist.

What can affect your result

  • Age: levels rise through childhood and puberty and drift down slowly in adult life
  • Sex: Labcorp gives separate ranges for males and females
  • Nutrition: fasting and caloric or protein restriction lower it
  • Liver, kidney and diabetes status
  • Growth hormone levels and growth hormone treatment
  • Assay platform: results from different assays aren't interchangeable
  • High-dose biotin can interfere with the assay
  • High-dose biotin (vitamin B7) can interfere with the assay. Labcorp advises stopping biotin at least 72 hours before the draw and Mayo asks for 12 hours, unless your clinician says otherwise.
  • Long fasting, poor nutrition and caloric or protein restriction lower IGFBP-3 (Labcorp, Quest).
  • Liver failure and poorly controlled diabetes lower it, and chronic kidney failure raises it (Labcorp).
  • IGFBP-3 assays vary a lot between platforms and manufacturers (Mayo). A change of lab or method can shift results, so compare trends from the same assay.
  • Rarely, antibodies to animal proteins (heterophile antibodies) can distort an immunoassay result (Mayo).

Any time of day. IGFBP-3 shows only minor fluctuation across the day (Mayo). IGFBP-3 bound to IGF-1 clears with a half-life of about 12 hours, so it gives a steadier picture than growth hormone itself (Mayo).

When to talk to a clinician

There is no emergency threshold for IGFBP-3. Talk with the clinician who ordered it if your result is outside your lab's range for your age and sex, especially if a child is growing slowly, or an adult notices growing hands or feet, changing facial features or joint pain. A result outside the range is a reason for a conversation, not an emergency.

Questions you could ask

  • Should IGFBP-3 be checked together with IGF-1?
  • Should follow-up tests use the same lab and method?
  • Does this result fit my age, and were IGF-1 and kidney function checked?
  • Could treatment or a supplement explain it?
  • Should we repeat it at the same lab?
  • Could nutrition, liver health or blood sugar control be affecting this number?

Questions people ask

Why check IGFBP-3 if I already had IGF-1?

IGFBP-3 carries IGF-1, and the two usually move together. Looking at both can help when growth hormone deficiency is a question or when treatment is being followed. For most uses, IGF-1 is the more informative of the two (Mayo).

Why do labs show such different ranges?

IGFBP-3 assays differ between platforms, and labs build ranges from different groups of people. Some labs split by sex and some don't. Compare your result with the range printed on your own report, and use the same lab for follow-up tests.

Can biotin change my result?

Yes, high-dose biotin (vitamin B7) can interfere with some assays. Labcorp's instructions say to stop biotin at least 72 hours before the draw and Mayo's say 12 hours. Follow your lab's instructions, and check with your clinician before changing any supplement.

Show the science and sources

Units

  • 1 mg/L = 1 mg/L
  • 1 mg/L = 1 µg/mL
  • 1 mg/L = 1000 µg/L

Open the IGFBP-3 unit converter

Is a change real?

IGFBP-3 naturally varies about 10.1% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 31% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Desirable Biological Variation Database specifications, 2014 update (Minchinela J, Ricos C, et al.; the 'Ricos database', a compilation of median published CVI/CVG).

For clinicians and researchers

IGFBP-3 is a 264-amino-acid protein of about 29 kDa, made mainly in the liver, and is the most abundant of the IGF-binding proteins (Mayo). It binds 75-90% of circulating IGF-1 in a ternary complex with IGF-1 and the acid-labile subunit (Labcorp). Quest reports that it carries about 95% of circulating IGF-I and IGF-II. Its synthesis is GH-dependent. Non-complexed IGFBP-3 has a half-life of 30-90 minutes and IGF-1 about 10 minutes, but the complex clears with a half-life of about 12 hours, so IGFBP-3 and IGF-1 show only minor fluctuation across the day and give a stable, integrated measure of GH production and tissue effect (Mayo). IGFBP-3 rises in early childhood and puberty and falls slightly in adult life. It decreases during fasting and chronic malnutrition and in hepatic failure and diabetes mellitus, and it increases in chronic renal failure (Labcorp). Labcorp uses an IDS-iSYS immunochemiluminometric assay with age- and sex-specific intervals from Friedrich et al. (2014). Mayo uses an Immulite 2000 chemiluminescent immunoassay, does not split by sex, and warns that results differ significantly between platforms and manufacturers, so a baseline should be re-established if the assay changes. Mayo notes that IGF-1 generally has better diagnostic sensitivity and specificity than IGFBP-3, that the two together are better than either alone for growth hormone deficiency and for monitoring treatment, and that in acromegaly IGFBP-3 adds little to IGF-1. Treatment aims are levels within the reference range, ideally the middle to upper third for replacement and the lower third for treated acromegaly. Mayo notes that IGFBP-3 can't be used reliably as a prognostic marker for breast, colon, prostate or lung cancer. Reported units include mg/L, µg/mL, µg/L and ng/mL (UnitsLab).

LOINC 2483-6 (primary), 33808-7. Specimen: serum.

Sources

  1. Insulin-like Growth Factor-binding Protein 3 (IGFBP-3) (test 140152), Labcorp
  2. IGFB3: Insulin-Like Growth Factor-Binding Protein 3, Serum, Mayo Clinic Laboratories
  3. IGF Binding Protein-3 (IGFBP-3) (test code 34458), Quest Diagnostics
  4. IGFBP-3 (preanalytical recommendations and reference values), Eurofins Biomnis
  5. Insulin-like growth factor binding protein 3 (IGFBP-3) conversion calculator, UnitsLab

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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