How Long Can IGF-1 Blood Samples Sit Before Testing?

What This Study Found

A new study tested how long IGF-1 blood samples stay accurate before being processed and measured in a lab. Researchers found that IGF-1 levels remained stable for at least 72 hours — about three days — no matter what temperature the sample was stored at or how long it sat before being spun down in a centrifuge. When samples were refrigerated at 4°C (standard fridge temperature), they stayed accurate for up to 7 days.

What Is IGF-1 and Why Does It Matter for Diabetes?

Insulin-like growth factor-1 (IGF-1) is a hormone made mostly in the liver. It works closely with insulin and growth hormone to help your body manage blood sugar, build muscle, and repair cells. In people with diabetes, IGF-1 levels can be affected by how well blood sugar is controlled over time. Doctors sometimes measure IGF-1 alongside other hormone tests to get a fuller picture of metabolic health.

Because IGF-1 is a peptide hormone — meaning it is made of proteins — researchers have long wondered whether it breaks down quickly after blood is drawn. Until now, there was very little data on this.

How the Study Was Done

Ten healthy adults each donated a small amount of blood. Samples were split into groups and stored at four different temperatures: frozen at -20°C, refrigerated at 4°C, room temperature (20–25°C), and warm room temperature (30°C). Some samples were processed right away, while others were left to sit for 8 or 24 hours before processing — mimicking what might happen in a busy clinic or during sample transport.

IGF-1 was measured at several time points: right away, then at 8, 24, 48, 72, 168, and 672 hours. Researchers used a threshold of 10.7% change from the original reading to decide whether a sample had become unreliable.

Key Results at a Glance

• 72 hours (3 days): IGF-1 stayed accurate at ALL temperatures, even with delayed processing
• 168 hours (7 days): Samples stored in the fridge at 4°C remained accurate, with less than 5.5% deviation
• 672 hours (28 days): Frozen samples at -20°C showed only a -1.5% change — essentially no meaningful drift

Why This Matters for Patients and Clinics

This research has real-world value. Blood samples are not always processed immediately. Samples from rural clinics, home blood draws, or busy hospital labs may sit for hours before reaching a testing machine. Knowing that IGF-1 is stable for at least three days — and up to a week when refrigerated — means clinicians and lab workers can feel more confident in test results even when there are delays.

For patients managing diabetes or hormone-related conditions, this means your IGF-1 result is less likely to be thrown off by a delay in processing. That is one less variable to worry about when you are tracking your metabolic health.

Important Limitations

This study used only 10 healthy adult participants, so results may not fully reflect people with diabetes or other conditions that affect hormone levels. More research with larger and more diverse groups would strengthen these findings.

If you are monitoring hormone health alongside your diabetes management, MDS Diabetes offers a range of diabetes testing and monitoring supplies to support your care routine. Visit mdsdiabetes.com to explore options that fit your lifestyle.

Full Citation

Louw, George, Khoza (2026). Short- and medium-term pre-analytical stability of human serum insulin-like growth factor-1. Clinical Chemistry and Laboratory Medicine. PMID: 41167200. DOI: 10.1515/cclm-2025-0868