One Patient's Switch: Moving From U-500 to a Concentrated Insulin in an Automated Pump

A 40-year-old man with Type 1 diabetes faced a practical problem: he had significant insulin resistance and was using regular U-500 insulin—a highly concentrated form—in his Tandem t:slim X2 automated insulin delivery system with Control IQ technology. U-500 is five times stronger than standard insulin, so it requires less volume. Still, he was refilling his insulin cartridge very frequently, which became burdensome.

His healthcare team decided to try switching him to insulin lispro U-200—another concentrated insulin, but one that is twice as strong as U-100 rather than five times as strong. To maintain his total daily insulin dose, he also started taking a separate injection of long-acting insulin each day. While this added an injection, it allowed him to use the pump with a less concentrated formula.

Three weeks after making the switch, his blood sugar control improved noticeably. His time in range—the percentage of day his glucose stayed in target—increased by 17 percentage points. The time his blood sugar ran high dropped by 16 percentage points. Time below range barely changed, staying near 0.1 percentage points lower. His glucose management indicator, which estimates average blood sugar, fell from 8.1% to 7.4%. After 24 months, he maintained this improved control.

It is crucial to understand that concentrated insulins like U-200 are not officially approved by the FDA for use in insulin pumps. The researchers emphasize that this approach should only be attempted by people whose healthcare providers have deep experience with pump therapy and can offer thorough education and ongoing support.

Insulin lispro U-200 does behave much like standard U-100 insulin in the body, which may make dose calculations more straightforward than with U-500. However, all pump settings must be carefully recalibrated when switching between insulin formulations. Anyone considering a similar change should not attempt it without direct guidance from their care team.

This single patient's experience suggests that insulin lispro U-200, when paired with external long-acting insulin, may offer a safer and more convenient alternative to U-500 for people with high insulin needs who use automated pumps. The change also improved his satisfaction with his diabetes management. That said, this is one person's story, not a proven solution for everyone. Anyone with similar insulin resistance should talk with their healthcare provider about whether this option might be worth exploring in their own situation.

Source: AACE endocrinology and diabetes. Evidence type: PubMed indexed literature. Type1Cure is an information and intelligence hub, not a medical advice service. This article summarizes published research and does not provide diagnosis, treatment, or personal medical guidance. Always talk to your own care team before changing anything about your Type 1 diabetes management.