Continuous Subcutaneous Insulin Infusion: Pump Settings and Safety

When you’re managing diabetes with an insulin pump, every setting matters. A tiny mistake in your basal rate or bolus calculation can send your blood sugar crashing-or soaring-within hours. This isn’t theory. It’s real life for thousands of people using continuous subcutaneous insulin infusion (CSII), and getting it right means knowing exactly how your pump works, what each setting does, and how to stay safe when things go wrong.

How Insulin Pumps Actually Work

Insulin pumps don’t replace your pancreas. They’re more like a precise, programmable drip system. Instead of injecting long-acting insulin once a day, you use only rapid-acting insulin-like Humalog or Novolog-delivered through a small tube under your skin. The pump gives you two kinds of insulin: a steady, low background dose (basal) and extra doses (bolus) for meals or high blood sugar.

Modern pumps don’t use long-acting insulins at all. That’s because rapid-acting insulin works fast and fades quickly, which gives you more control. You can adjust your basal rate every hour, turn it up if you’re sick, or drop it before a run. It’s flexibility you can’t get with injections.

But here’s the catch: this flexibility only helps if you set it up right. A pump set wrong can be more dangerous than no pump at all.

Setting Your Basal Rates: The Foundation of Safety

Your basal rate is the silent backbone of your therapy. It’s the insulin your body needs just to keep going-breathing, thinking, digesting-when you’re not eating. Most people need different amounts at different times. Maybe you need more insulin at 3 a.m. because of the dawn phenomenon, or less after your evening walk.

Start by figuring out your total daily insulin dose. Then, split it: 40-50% goes to basal, the rest to boluses. But don’t just divide it evenly. Basal rates usually change every 1-3 hours. A typical profile might look like this:

• 12 a.m. - 4 a.m.: 0.8 units/hour
• 4 a.m. - 8 a.m.: 1.2 units/hour
• 8 a.m. - 12 p.m.: 0.9 units/hour
• 12 p.m. - 6 p.m.: 1.0 units/hour
• 6 p.m. - 12 a.m.: 0.7 units/hour

To test your basal rate, fast for 24 hours. No food, no correction boluses, no exercise. Check your blood sugar every 2-3 hours. If it rises more than 1 mmol/L (18 mg/dL), your basal is too low. If it drops, it’s too high. Do this on different days to find your true pattern.

Dr. John Walsh, author of Pumping Insulin, says the most common pump error? Skipping basal testing. People guess. They don’t test. And then wonder why their numbers are all over the place.

Bolus Settings: Meals, Corrections, and the Hidden Math

When you eat, you need more insulin. That’s the bolus. But it’s not just one number. You need two key settings:

• Insulin-to-carbohydrate ratio (ICR): How many units of insulin you need per gram of carbs. A common starting point is 1 unit per 10-15g of carbs, but it varies wildly. One person might need 1 unit per 8g; another might need 1 unit per 20g.
• Insulin sensitivity factor (ISF): How much 1 unit of insulin lowers your blood sugar. For most adults, it’s 1 unit = 2-4 mmol/L (36-72 mg/dL). But if you’re insulin resistant, it could be 1 unit = 1 mmol/L.

Most pumps calculate boluses automatically. You enter your carbs and current blood sugar, and the pump says, “Give 3.2 units.” But if your ICR or ISF is off, the pump will give you the wrong dose every time.

There’s also a third type of bolus: the extended or dual-wave. High-fat meals-like pizza or a creamy pasta dish-digest slowly. A regular bolus spikes insulin too early, then crashes hours later. An extended bolus spreads the dose over 2-4 hours. A dual-wave gives half right away, half over time. Many people don’t use these, and end up with late-night highs.

Infusion Sets and Site Care: Don’t Ignore the Tube

Your pump is only as good as the cannula under your skin. Change your infusion set every 2-3 days. No exceptions. Leaving it in longer? That’s how you get infections, lipohypertrophy (fatty lumps), and blocked lines.

Rotate sites: abdomen, thighs, upper arms, lower back. Don’t reuse the same spot every time. A 2022 study found 27% of new pump users developed lipohypertrophy because they kept injecting in the same place.

Check your site every morning. If it’s red, swollen, painful, or leaking, change it immediately. Even a tiny kink in the tubing can stop insulin flow. And if insulin stops flowing for more than 2 hours, you’re at risk for diabetic ketoacidosis (DKA). That’s not rare. On Reddit’s r/diabetes, users report DKA developing in just 2-4 hours after an unnoticed disconnection.

Safety Protocols: What to Do When Things Go Wrong

Insulin pumps don’t turn off automatically if you pass out. They keep pumping. That’s why safety isn’t optional-it’s survival.

• Hypoglycemia: If your blood sugar drops and stays low, remove the pump. Treat with glucose tablets or juice. Don’t wait for it to fix itself.
• Hyperglycemia + ketones: If your blood sugar is above 14 mmol/L (250 mg/dL) and you have ketones, don’t just bolus more. Check your infusion set. Replace it. Flush the tubing. If ketones don’t drop in 2 hours, call your doctor.
• During surgery: For minor procedures where you’ll eat soon, you can keep the pump on-if your site is accessible and your glucose is between 4-12 mmol/L. For major surgery? Stop the pump. Switch to IV insulin.
• Postpartum: After giving birth, insulin needs drop sharply. Many women need to reduce their basal rate by 10-20% right away. If you’re breastfeeding, you might need to cut it even more.

The NIH warns: if someone using a pump becomes unconscious, treat it like a medical emergency. They need help fast-because the pump doesn’t know they’re down.

Advanced Features and New Tech

Modern pumps aren’t just pumps anymore. The Medtronic MiniMed 670G and Tandem Mobi are hybrid closed-loop systems. They adjust basal insulin automatically based on your CGM readings. But they still need you to tell them when you eat. They’re not magic.

The Omnipod 5 works with multiple CGMs, not just one brand. That’s a big deal. You’re not locked into one system anymore.

The Tandem Mobi, released in 2023, is the smallest pump on the market-about the size of a large coin. It’s designed for kids, with big buttons and simple menus. But even the simplest pump needs proper setup.

Next up? Bihormonal pumps that deliver both insulin and glucagon. They’re still in trials. But they could be the closest thing to an artificial pancreas we’ve seen.

Training and Real-World Challenges

You can’t just get a pump and go. The American Association of Clinical Endocrinologists says you need at least 15 hours of structured training before starting. That includes:

• How to insert a cannula
• How to program basal rates
• How to calculate boluses
• How to troubleshoot alarms
• How to handle emergencies

Most people get the basics in 2-4 weeks. But mastering extended boluses, temporary basals, and insulin-on-board (IOB) calculations? That takes 3-6 months.

And the biggest hurdle? Carbohydrate counting. A 2021 study found 38% of high blood sugar episodes in pump users were caused by miscounting carbs. You can have the best pump in the world, but if you think a slice of bread is 10g of carbs when it’s actually 25g, you’re going to be in trouble.

Cost, Access, and the Future

In the U.S., insulin pump therapy costs $6,500-$8,200 a year. That’s pump, supplies, and insulin. Multiple daily injections? $4,800-$5,500. Insurance helps, but gaps remain.

Adoption is growing. About 30% of people with type 1 diabetes in the U.S. use pumps. Among teens and young adults? It’s 45%. For those over 65? Only 22%. The gap isn’t just about tech-it’s about support. Older adults often lack the training or help they need.

By 2028, the American Diabetes Association predicts 40% of type 1 patients will be on pumps. But that won’t happen unless access and education improve.

What You Need to Do Today

If you’re on a pump:

1. Test your basal rate this week. Fast for 24 hours. Track your numbers.
2. Check your infusion set. Is it older than 72 hours? Change it.
3. Review your ICR and ISF. Are they based on real data-or just a guess?
4. Carry backup: extra infusion sets, insulin, batteries, glucose tabs.
5. Know your emergency plan. If you can’t reach your care team, who do you call?

If you’re thinking about starting:

• Get trained. Don’t skip it.
• Ask for a pump educator who’s seen hundreds of patients.
• Don’t believe the hype. Pumps aren’t easy. They’re powerful-but they demand your attention.

Insulin pumps give you freedom. But freedom comes with responsibility. Get the settings right. Stay vigilant. Your next meal, your next night’s sleep, your next day-all of it depends on it.

Insulin pumps are powerful tools-but they’re not magic. They require knowledge, discipline, and constant attention. Get the settings right. Test often. Change your site. Know your limits. And never stop learning.