U-100 Insulin: What It Is, How It’s Used, and What You Need to Know

When you hear U-100 insulin, the most common form of insulin used in the U.S., with 100 units of insulin per milliliter of fluid. Also known as standard insulin, it’s the baseline for most prescriptions, pens, and vials you’ll see at the pharmacy. If you’re managing diabetes, this is likely the insulin you’re using every day—whether you’re taking it with a syringe, pen, or pump. It’s not the strongest, and it’s not the weakest—it’s just the one most doctors prescribe because it’s predictable, widely available, and works well for most people.

But U-100 insulin isn’t the only kind out there. There’s U-500, which is five times stronger, and U-200, which packs more insulin into less volume. Mixing them up by accident can be deadly. That’s why knowing exactly what’s in your bottle matters. If you’re traveling, insulin injection, the method most people use to deliver U-100 insulin under the skin needs special handling—TSA lets you carry it through security, but you’ve got to pack it right. And if you’re storing it at home, heat and light can ruin it fast. Refrigeration isn’t always required, but it helps keep it stable longer.

U-100 insulin also plays a role in how you manage your daily life. If you’re a senior taking multiple meds, switching to a combo pill might help reduce your pill burden—but insulin isn’t one of those pills. It’s still injected, and that means you need to stay consistent. If you’re pregnant, breastfeeding, or caring for a child with diabetes, the same U-100 insulin is used—but dosing changes, and timing matters even more. You can’t just guess. That’s why monitoring your blood sugar and keeping a log helps you spot patterns before they turn into problems.

Some people think U-100 insulin is outdated because newer forms exist. But it’s not. It’s the foundation. Most insulin pens, whether brand or generic, are built for U-100. Most insurance plans cover it. Most pharmacies stock it. And if you’re flying, insulin storage, how you keep insulin safe during travel—whether it’s in a cooler, an insulated bag, or just your carry-on is part of the routine. You don’t need a special permit. You just need to know the rules.

What you’ll find below are real-world guides that tie directly to U-100 insulin. How to carry it on a plane. How to avoid mixing it up with other types. How to store it when you’re on the go. How to handle it safely if you’re a parent, a traveler, or someone juggling multiple medications. These aren’t theory pieces—they’re the kind of advice you need before you open that vial or load that pen.