When you start insulin pump therapy, your provider programs a handful of settings into the device, and those settings quietly drive nearly everything the pump does. Terms like basal rate, insulin-to-carb ratio, and correction factor can sound technical and intimidating at first, but understanding what each one means makes you a far more confident and capable pump user. This guide breaks down the core pump settings in plain language, so you understand what's happening behind the screen and can have more productive conversations with your care team.
The Core Insulin Pump Settings Explained
According to a review of insulin pump therapy published in PubMed Central, there are a few main settings that need to be programmed into an insulin pump, since the pump holds and delivers only rapid-acting insulin. Here's what each one does:
- Basal rate: The continuous background insulin the pump delivers, programmed as an hourly rate. It covers the glucose your body produces between meals and overnight. Many people have several different basal rates across the day.
- Insulin-to-carbohydrate ratio (carb ratio): How many grams of carbohydrate one unit of insulin covers. Written like 1:10, meaning one unit covers 10 grams of carbs. Used to calculate mealtime boluses.
- Correction factor (insulin sensitivity factor): How much one unit of insulin lowers your blood glucose. Used to calculate correction doses when glucose is above target.
- Target glucose: The blood glucose level the pump aims for when calculating a correction dose.
- Active insulin time (insulin on board): How long the pump considers a previous dose to still be working, which prevents stacking doses too closely together.
These settings work together every time you bolus, and they're individualized to you. What's right for one person may be completely wrong for another, which is why they're prescribed and adjusted by your care team.
Basal Rates: Your Background Insulin
Basal insulin is the foundation of pump therapy, and understanding it helps explain why pumps offer such fine-tuned control compared to injections.
Your basal rate is the slow, continuous trickle of rapid-acting insulin the pump delivers around the clock to manage the glucose your liver releases between meals and during sleep. Because it's programmed as an hourly rate, the pump can deliver different amounts at different times of day. This is a major advantage over long-acting injected insulin, which delivers a relatively fixed amount. The PubMed Central review notes that when starting pump therapy, basal insulin typically represents around half of the total daily insulin dose, though more recent research published in PubMed Central suggests the appropriate proportion may be closer to 30 to 40% for many people.
The ability to set multiple basal rates matters because insulin needs aren't constant. Many people need more basal insulin in the pre-dawn hours to counter the dawn phenomenon (the natural early-morning glucose rise) and less during the afternoon or during physical activity. Your care team uses your glucose patterns, often gathered from a CGM, to fine-tune these rates over time.
One feature worth knowing about is the temporary basal rate. The PubMed Central review notes that a temporary modification of usual basal delivery may be useful on sick days or during exercise. For example, you might reduce your basal rate before a workout to lower the risk of exercise-induced lows, or increase it during illness when insulin needs often rise. If you use an automated insulin delivery system like the Tandem t:slim X2 with Control-IQ or the Omnipod 5, the system automatically adjusts your basal delivery based on CGM readings, though your underlying programmed rates still serve as the starting point.
Carb Ratio and Correction Factor: Calculating Your Boluses
While basal insulin runs in the background, the carb ratio and correction factor handle your mealtime and correction doses. These are the settings your pump's bolus calculator uses every time you eat or correct a high.
The insulin-to-carbohydrate ratio determines your mealtime dose. As the PubMed Central review illustrates, if you eat a meal containing 20 grams of carbohydrate and your ratio is 1 unit per 10 grams, the pump calculates a 2-unit dose. Your ratio may differ at different meals, since many people are more insulin-resistant in the morning and need a more aggressive ratio at breakfast than at dinner. When you enter your carb count, the pump does the math automatically using this setting.
The correction factor, also called the insulin sensitivity factor, determines how much insulin you need to bring a high glucose back to target. It represents how many points one unit of insulin will lower your blood glucose. For example, if your correction factor is 1 unit per 50 mg/dL and your glucose is 50 points above target, the pump calculates a 1-unit correction. When you bolus for a meal while your glucose is also high, the pump combines the meal dose and the correction dose into a single recommendation.
Interestingly, research published in PubMed Central analyzing real-world Control-IQ users found that the correction factor setting may be the single most impactful setting for optimizing time in range, with a more aggressive correction factor associated with higher time in range and only a negligible effect on hypoglycemia. This is a useful reminder that these settings are powerful levers, which is exactly why they should only be adjusted with your care team's guidance rather than on your own.
Finally, the active insulin time setting (also called insulin on board) tells the pump how long a previous dose is still working. This prevents the pump from recommending another correction on top of insulin that hasn't finished acting yet, which helps protect against stacking doses and causing a low. It's completely normal to find all of these interacting settings confusing at first, and your diabetes care and education specialist can walk you through them as many times as you need.
Why Understanding Your Settings Makes You a Better Pump User
You don't need to set your own pump parameters, and you shouldn't, but understanding what they do transforms your relationship with your pump. When you know that your basal rate covers background needs, your carb ratio handles meals, and your correction factor addresses highs, you can recognize patterns, ask better questions, and partner more effectively with your care team when something needs adjusting. Insulin needs change constantly due to growth, weight changes, activity, stress, illness, and countless other factors, so your settings will be revisited over time. The PubMed Central research is clear that even experienced clinicians don't always agree on the exact right adjustment, which underscores that this is collaborative, iterative work, not a one-time setup. At Adapt Health Diabetes, we provide the pumps and supplies that make this fine-tuned management possible. Visit our Education page and Learning Center for more guides on insulin pump therapy.
Frequently Asked Questions About Insulin Pump Settings
Can I adjust my own pump settings?
You should not adjust your basal rates, carb ratios, or correction factors on your own without guidance from your healthcare provider. These settings directly control how much insulin you receive, and incorrect changes can lead to dangerous highs or lows. Your care team uses your glucose data to make informed adjustments. That said, understanding what each setting does helps you recognize when something might need attention and have a productive conversation with your provider. Some temporary adjustments, like setting a temporary basal rate for exercise, may be something your care team trains you to do within defined limits.
Why do I have different basal rates at different times of day?
Insulin needs naturally vary across the day. Many people need more basal insulin in the early morning hours to counteract the dawn phenomenon, a natural glucose rise driven by hormones, and less during the afternoon or during periods of activity. Programming multiple basal rates lets the pump match your background insulin to these changing needs, which is one of the key advantages of pump therapy over a single daily long-acting injection. Your care team determines your basal pattern based on your individual glucose trends.
What's the difference between my carb ratio and my correction factor?
Your carb ratio is used for food: it tells the pump how much insulin to deliver based on the carbohydrates you're eating. Your correction factor is used for highs: it tells the pump how much insulin to deliver to bring an above-target glucose back down. When you bolus for a meal while also running high, the pump uses both settings together, calculating a meal dose plus a correction dose and combining them into one recommendation. Both settings are individualized and prescribed by your care team.
Why does my pump sometimes recommend less insulin than I expect?
This is often due to the active insulin time, or insulin on board, setting. The pump tracks how much of your previous doses is still working and subtracts that from any new correction recommendation. This prevents stacking, where doses pile up too closely together and cause a low. So if you recently bolused, the pump may recommend a smaller correction because it knows insulin from the earlier dose is still active. This is a safety feature working as intended.
Do automated insulin delivery systems still use these settings?
Yes. Even on AID systems like the Tandem t:slim X2 with Control-IQ, the Omnipod 5, or the Medtronic MiniMed 780G, your programmed settings serve as the foundation the algorithm builds on. The system automatically adjusts basal delivery and may deliver automatic corrections based on CGM data, but it still uses your carb ratio for meal boluses and your other settings as algorithm inputs. Getting these underlying settings right remains important even with automation, which is why your care team continues to review them.
Get the Pump Supplies That Keep Your System Running
Whichever pump you use, Adapt Health Diabetes delivers the infusion sets, cartridges, and CGM supplies that keep it working, all through your insurance. Browse our full range of pump supplies from Tandem Diabetes, Medtronic MiniMed, and Beta Bionics, or visit our Resources page. Questions? Contact our team.
This article is for educational purposes only and does not replace professional medical advice. Never adjust your insulin pump settings without guidance from your healthcare provider or diabetes care team.
Sources
- Pickup JC. Insulin Pumps in General Practice. PubMed Central. 2018.
- Walsh J, et al. A Review of Insulin-Dosing Formulas for Continuous Subcutaneous Insulin Infusion (CSII) for Adults with Type 1 Diabetes. PubMed Central. 2016.
- Pinsker JE, et al. Therapy Settings Associated with Optimal Outcomes for t:slim X2 with Control-IQ Technology in Real-World Clinical Care. PubMed Central. 2023.
