Continuous Subcutaneous Insulin Infusion: Pump Settings and Safety Tips for Daily Use

Getting an insulin pump isn’t like switching from a flip phone to a smartphone. It’s more like learning to fly a small plane-every setting matters, and one wrong move can have serious consequences. Continuous Subcutaneous Insulin Infusion (CSII), or insulin pump therapy, gives you precise control over your insulin, but only if you understand how to use it right. This isn’t about convenience alone. It’s about staying safe, avoiding dangerous highs and lows, and making sure your body gets exactly what it needs-every hour, every meal, every day.

How Insulin Pumps Actually Work

Insulin pumps don’t deliver long-acting insulin. They use only rapid-acting analogs like Humalog (insulin lispro) or Novolog (insulin aspart). That’s because they’re designed to mimic how a healthy pancreas works: a steady trickle of insulin all day (basal rate), plus bursts for meals (bolus). Without long-acting insulin, you’re not stuck with one dose lasting 24 hours. You can adjust your insulin minute by minute.

The pump connects to your body through a small tube and cannula inserted under the skin-usually in the abdomen, thigh, or upper arm. You change this site every 2-3 days. Why? Because leaving it in longer increases your risk of infection, poor absorption, and lipohypertrophy-those lumpy, scarred areas where insulin doesn’t work well. A 2022 study found that 32% of new pump users had site reactions within the first three months. That’s why changing your site on time isn’t optional. It’s essential.

The Three Key Settings You Must Get Right

There are three numbers that control your entire pump therapy: basal rate, insulin-to-carbohydrate ratio (ICR), and insulin sensitivity factor (ISF). Mess up any one of these, and your blood sugar will swing wildly.

• Basal rate: This is your background insulin. It’s usually 40-50% of your total daily dose, spread out over 24 hours. Most people need more insulin in the early morning (due to the dawn phenomenon) and less overnight. Pumps let you set different rates for each hour. If you’re waking up with high blood sugar every day, your morning basal might be too low. If you’re crashing at 3 a.m., it’s too high.
• Insulin-to-carbohydrate ratio (ICR): This tells the pump how much insulin you need for each gram of carbs. A common starting point is 1 unit per 10-15 grams of carbs, but that varies wildly. One person might need 1 unit for 8 grams of carbs, another for 20. Test it by eating a known amount of carbs (say, 30g) with no insulin on board, then check your blood sugar 2-3 hours later. If it’s up 3 mmol/L, you need more insulin. If it’s down 2 mmol/L, you need less.
• Insulin sensitivity factor (ISF): Also called the correction factor, this tells the pump how much 1 unit of insulin lowers your blood sugar. For most adults, it’s around 1 unit per 2-3 mmol/L. If your blood sugar is 12 mmol/L and your target is 6 mmol/L, you’re 6 mmol/L high. If your ISF is 1:3, you’d need 2 units to correct it. But if your ISF is wrong-say, you think it’s 1:3 but it’s really 1:2-you’ll underdose and stay high.

These settings aren’t set-and-forget. They change with weight, activity, stress, illness, and even the season. A 2021 study in Diabetes Care found that 38% of hyperglycemia episodes in pump users were due to incorrect carb counting or outdated ICRs. That’s why you need to retest your settings every few months-or whenever your routine changes.

Bolus Types: When to Use Immediate, Extended, or Dual-Wave

Not all meals are created equal. A slice of pizza and a bowl of rice affect your blood sugar in totally different ways.

• Immediate bolus: Use this for meals high in carbs and low in fat or protein-like toast, pasta, or fruit. The insulin hits fast and matches the carb spike.
• Extended bolus: Use this for high-fat meals like pizza, burgers, or creamy pasta. Fat slows digestion, so carbs enter your blood over 3-6 hours. Giving all the insulin upfront means you crash after 2 hours, then spike later. An extended bolus spreads the dose over 2-4 hours.
• Dual-wave bolus: This combines both. Use it for meals like a sandwich with cheese and mayo, or a burrito. Give 60% upfront and 40% over 2 hours. Most pumps let you set this easily. If you’re still high 4 hours after eating, you probably need more extended insulin.

Insulin on board (IOB)-also called active insulin-is your pump’s built-in safety feature. It tracks how much insulin is still working in your body from your last bolus. If you bolus again too soon, the pump will subtract the active insulin and give you less. This prevents stacking insulin and crashing. But if you turn off IOB or ignore it, you’re gambling with your blood sugar.

Safety First: What Can Go Wrong-and How to Stop It

Insulin pumps are reliable, but they’re not foolproof. The biggest danger? Not knowing when something’s broken.

Here’s what you need to watch for:

• Infusion set disconnection: If the tube comes loose or the cannula kinks, insulin stops flowing. You can go into diabetic ketoacidosis (DKA) in as little as 2-4 hours. That’s why you check your pump every time you check your blood sugar. Look at the screen: Is it showing “No Delivery”? Is the reservoir full? Is the tubing kinked? Always carry backup supplies-extra infusion sets, insulin, syringes, and glucose tabs.
• Hypoglycemia: If your blood sugar drops below 4 mmol/L and you’re not eating, stop the pump. Remove the cannula. Treat with 15g of fast-acting carbs. Don’t wait for it to get worse. If you’re unconscious, someone else must act-your pump won’t stop on its own unless it’s a closed-loop system.
• Overcorrection: People often bolus too much because they’re scared of high numbers. But if you’re already low on insulin (say, after exercise), another big bolus can send you crashing. Always check IOB before correcting.
• Illness or stress: When you’re sick, your body needs more insulin-even if you’re not eating. Your basal rate might need to go up by 20-50%. Don’t skip it because you’re not hungry. Use your ISF to correct highs, and check ketones if your blood sugar stays above 13 mmol/L for more than 2 hours.

And never, ever skip glucose checks. The American Diabetes Association says you need at least four checks a day. But if you’re new to the pump, or you’re sick, or you’ve just changed your settings-check every 2 hours. You can’t manage what you don’t measure.

Special Situations: Surgery, Pregnancy, and Travel

Life doesn’t pause for your pump. Here’s how to handle big changes.

• Surgery: For minor procedures where you’ll eat within a few hours, you can keep the pump on-if your site is accessible, your batteries are fresh, and your blood sugar is between 4-12 mmol/L. For major surgery or fasting longer than 6 hours, switch to IV insulin. Your pump won’t know you’re not eating. It’ll keep delivering insulin-and you could crash.
• Postpartum and breastfeeding: After delivery, insulin needs drop sharply. Most women need to reduce their basal rate by 20-40% right away. If you’re breastfeeding, you might need to cut it another 10-20% as milk production ramps up. Don’t guess. Test often. Talk to your diabetes team.
• Travel: Time zones? Adjust your basal schedule gradually. Don’t change it all at once. Carry twice as many supplies as you think you’ll need. Keep insulin cool but not frozen. Bring a backup syringe. And always wear a medical ID bracelet that says “Insulin Pump User.”

Who Should-and Shouldn’t-Use a Pump

Insulin pumps aren’t for everyone. The American Diabetes Association says you need to be able to:

• Count carbs accurately
• Check blood sugar at least four times a day
• Understand how insulin works
• Be willing to troubleshoot problems

If you can’t do those things, a pump will make things harder-not easier. People with severe hypoglycemia unawareness should only use pumps with automatic low-glucose suspend features. And if you’re unwilling to learn the settings, don’t get one. As Dr. Anne Peters says, “CSII is not an artificial pancreas. It demands active patient engagement.”

And here’s something most people don’t realize: pumps aren’t magic. A 2023 study in the T1D Exchange Registry found that 68% of users saw their A1c drop by at least 0.5% in six months. But 45% had at least one pump failure in their first year. Success isn’t about the device. It’s about your commitment.

What’s New in 2025

The pump world is moving fast. The Tandem Mobi, released in 2023, is the smallest pump ever-perfect for kids. The Omnipod 5 is now interoperable, meaning it can work with different CGMs, not just one brand’s. And new systems are extending automatic insulin suspension from 30 minutes to 120 minutes during low blood sugar events.

Next up? Bihormonal pumps that deliver both insulin and glucagon. These could stop lows before they happen. But they’re still years away from being widely available.

For now, the best pump is the one you use consistently, safely, and with full understanding. Technology helps. But your knowledge? That’s what keeps you alive.

Using an insulin pump successfully means treating it like a tool-not a cure. It doesn’t think for you. It doesn’t guess. It follows your instructions. So learn the settings. Test them often. Trust your numbers. And never skip the basics: check your site, watch your carbs, and always have a backup plan.