An insulin pump is a small electronic device that delivers rapid-acting insulin continuously through a thin cannula placed under the skin. It replaces multiple daily injections by providing both a basal rate (continuous background drip) and bolus doses on demand for meals and correction. Modern pumps integrate with continuous glucose monitors to form hybrid closed loop systems that automatically adjust insulin every 5 minutes based on glucose readings. Pumps are used primarily in type 1 diabetes, with growing use in type 2 diabetes on insulin.
Components of an Insulin Pump
- Pump body — battery-powered device with screen, buttons, and motor
- Reservoir or cartridge — holds 200 to 300 units of rapid-acting insulin
- Infusion set — tubing plus the cannula that goes under the skin (in tubed pumps)
- Pod — all-in-one integrated unit (in tubeless pumps like Omnipod)
- Cannula — soft Teflon or steel tube that delivers insulin into subcutaneous fat
- Adhesive patch — keeps the infusion set or pod on the skin
- Controller — for tubeless pumps, a separate handheld device or smartphone app
How the Pump Delivers Insulin
The pump’s small motor pushes the plunger of the reservoir tiny amounts every few minutes, delivering insulin through the tubing or pod and out of the cannula into subcutaneous fat. There are two patterns of delivery:
- Basal rate — a continuous background drip programmed in units per hour, often with multiple rates across the day (for example 0.6 U/hr from 6 AM to noon, 0.4 U/hr noon to 6 PM, 0.5 U/hr overnight)
- Bolus dose — a larger on-demand dose taken for meals (calculated from carbs and current glucose) or to correct high blood sugar
Together basal and bolus replicate the normal pancreas — small continuous secretion plus meal-time spikes.
Basal vs Bolus — Quick Comparison
| Feature | Basal | Bolus |
|---|---|---|
| Purpose | Background coverage between meals and overnight | Cover meal carbohydrates or correct high glucose |
| Delivery | Continuous tiny amounts every few minutes | Larger amount over seconds to minutes |
| Programming | Set rates per hour, fixed in pump | Calculated per dose by user or app |
| Typical share of total daily insulin | 40 to 50 percent | 50 to 60 percent |
| Common adjustments | Temp basal for exercise, illness, dawn phenomenon | Extended bolus for high-fat meals, dual-wave for mixed meals |
Tubed vs Tubeless (Patch) Pumps
| Feature | Tubed (Tandem, Medtronic) | Tubeless (Omnipod) |
|---|---|---|
| Where pump body sits | Clipped to belt, pocket, or clothing | Directly on skin as a pod |
| Tubing | 23 to 43 inches typical (2 inches on Mobi) | None — integrated cannula |
| Reservoir size | 200 to 300 units | 200 units |
| Site change | Every 2 to 3 days (set); reservoir every 3 days | Every 3 days (whole pod) |
| Showering or swimming | Disconnect for shower; swim depends on model | Wear continuously; waterproof IPX8 |
| Control | Buttons on pump (some with phone app) | Handheld controller or smartphone |
| Examples | Tandem t:slim X2, Tandem Mobi, Medtronic 780G | Omnipod 5 |
Pump-Compatible Insulins
Only rapid-acting insulins are used in pumps:
- Humalog (insulin lispro) — onset 15 min, peak 1 to 2 hr, duration 3 to 5 hr
- Novolog (insulin aspart) — onset 10 to 20 min, peak 1 to 3 hr, duration 3 to 5 hr
- Apidra (insulin glulisine) — onset 15 min, peak 1 to 1.5 hr, duration 3 to 4 hr
- Fiasp (faster aspart) — onset under 5 min, peak 1 to 2 hr, duration 3 to 5 hr
- Lyumjev (faster lispro) — onset under 5 min, peak 1 to 2 hr, duration 3 to 5 hr
Long-acting insulins (Tresiba, Lantus, Toujeo, Levemir) are not used in pumps — the pump itself provides the continuous low-dose function those insulins serve in injection regimens.
Programmable Features
- Multiple basal rates — typically 4 to 12 rates across 24 hours; common pattern is higher rates 4 to 8 AM (dawn phenomenon) and lower mid-afternoon
- Temporary basal rate — increase or decrease basal for hours (exercise, illness, alcohol)
- Extended bolus — deliver part of bolus immediately, part over 1 to 4 hours (high-fat meals)
- Dual-wave bolus — partial immediate bolus plus extended portion
- Insulin-on-board (IOB) tracking — pump remembers active insulin to prevent stacking
- Carb counting calculator — built-in bolus calculator from carb input and current glucose
- Multiple personal profiles — weekday vs weekend, sick day, exercise day
Hybrid Closed Loop (AID) Integration
Modern pumps pair with continuous glucose monitors and use control algorithms to automatically adjust insulin every 5 minutes based on glucose readings. Currently approved hybrid closed loop systems in the US (2026) include:
| System | Pump | CGM | Algorithm | Target |
|---|---|---|---|---|
| Tandem Control-IQ | t:slim X2, Mobi | Dexcom G6, G7 | Control-IQ | 112.5 mg/dL fixed |
| Medtronic SmartGuard | MiniMed 780G | Guardian 4 | SmartGuard with auto-correction | 100, 110, or 120 mg/dL |
| Omnipod 5 | Pod (tubeless) | Dexcom G6, G7, Libre 2 Plus | SmartAdjust | 110-150 mg/dL adjustable |
| Beta Bionics iLet | iLet | Dexcom G6, G7 | iLet bionic pancreas | Adaptive, no manual carb count |
Benefits vs Multiple Daily Injections
- Fewer injections — one cannula every 2 to 3 days vs 4 to 6 injections daily
- Variable basal rates — handles dawn phenomenon better
- More flexible meal timing — extended boluses for high-fat meals
- Exercise adjustments — temporary basal can prevent low blood sugar
- Improved time in range — pump plus CGM users average 70 to 75 percent TIR vs 50 to 60 percent with MDI
- Reduced hypoglycemia — AID systems suspend or reduce basal automatically as glucose falls
- Better A1C in many users — average reduction 0.5 to 1.0 percentage point
Drawbacks and Considerations
- More equipment to learn and maintain
- Site changes every 2 to 3 days
- Higher upfront and ongoing costs
- Risk of pump failure or cannula kink leading to no insulin delivery (rapid onset DKA)
- Need to disconnect for some activities
- Body image considerations — visible patch or tubing
- Alarms and notifications can be disruptive
- Learning curve of weeks to months
Site Care and Rotation
- Rotate sites among abdomen, upper outer thighs, upper buttocks, upper outer arms
- Move at least 1 inch from previous site each change
- Avoid scar tissue, bony areas, waistband, and existing lipohypertrophy
- Inspect site daily for redness, leaking, or tenderness
- Use barrier wipes (Skin-Tac, Mastisol) if adhesive struggles
- Use barrier films (IV3000, Tegaderm) under sets for sensitive skin
- Always have backup insulin pen or syringe in case of pump failure
Indications and Candidates
- Type 1 diabetes (primary indication)
- Type 2 diabetes on intensive insulin (multiple daily injections), with high A1C or hypoglycemia problems
- Children — Omnipod 5 from age 2, Tandem Control-IQ from age 6, Medtronic 780G from age 7
- Adults with dawn phenomenon poorly controlled by injections
- Athletes wanting fine-grained insulin adjustment
- Pregnant women with type 1 diabetes (often improved control on pump)
Side Effects and Risks
- Diabetic ketoacidosis — pumps deliver no long-acting insulin; any interruption (cannula kink, dislodged pod, empty reservoir) rapidly leads to hyperglycemia and ketones
- Hypoglycemia — risk from over-bolusing or basal that exceeds need; AID systems greatly reduce this
- Infusion site infection — rare; redness, warmth, pus needs same-day care
- Skin reactions to adhesive — itching, rash, peeling; barrier products help
- Lipohypertrophy or scarring — from inadequate site rotation
- Pump malfunction — rare; backup insulin always required
Related Reading
For specific pump models see our guides on Omnipod 5, Medtronic 780G, and Tandem Mobi. For the broader category see hybrid closed loop systems. For insulin context see insulin therapy and all treatment options.
External Resources
The American Diabetes Association Standards of Care 2024 covers pump indications and use, and the ISPAD 2022 Guidelines include pediatric pump-specific recommendations.
The Bottom Line
An insulin pump is a small battery-powered device that delivers continuous rapid-acting insulin through a thin cannula placed under the skin. It provides two delivery patterns — basal (continuous tiny background drip) and bolus (on-demand doses for meals and corrections) — to mimic the normal pancreas. Pumps come in two main form factors: tubed (Tandem t:slim X2, Tandem Mobi, Medtronic 780G) and tubeless patch (Omnipod 5). Modern pumps integrate with continuous glucose monitors to form hybrid closed loop systems that automatically adjust insulin every 5 minutes — including Tandem Control-IQ, Medtronic SmartGuard, Omnipod 5 SmartAdjust, and Beta Bionics iLet. Pumps improve time-in-range and reduce hypoglycemia compared with multiple daily injections, especially with AID integration. They also add learning curve, equipment, cost, and the risk of rapid DKA if insulin delivery is interrupted. Talk to your clinician and diabetes educator about whether a pump fits your goals, lifestyle, and access to support.
