A Tandem pump is an insulin pump made by Tandem Diabetes Care, designed for people with type 1 diabetes who need continuous insulin delivery throughout the day. What sets Tandem apart from older pump designs is its touchscreen interface, rechargeable battery, and built-in software that can automatically adjust insulin delivery based on real-time glucose readings from a continuous glucose monitor (CGM). The company currently makes two models: the t:slim X2 and the newer, smaller Tandem Mobi.
How the t:slim X2 Works
The t:slim X2 is Tandem’s flagship pump. It has a color touchscreen with a capacitive touch panel, similar to a smartphone, which replaced the button-heavy interfaces of earlier insulin pumps. Inside, three separate microprocessors handle pump functions and wireless communication. A small motor and rack drive mechanism push insulin from a cartridge that holds up to 300 units (3 mL) of U-100 insulin.
The pump connects to your body through a thin tube called an infusion set, which delivers insulin under the skin. A USB port on one end of the device, protected by a rubber cover, handles charging. The battery typically lasts four to seven days on a single charge depending on how many features you use. If you run both a CGM connection and the mobile app, expect closer to four days. Tandem recommends plugging it in for 10 to 15 minutes daily to keep the battery healthy.
The t:slim X2 is FDA-approved for people with type 1 diabetes aged 6 and older.
The Tandem Mobi
The Mobi is Tandem’s smaller, newer pump designed for people who want something less visible. It measures just over 2 inches long, about 1.5 inches wide, and half an inch thick, weighing only 1.06 ounces with a full reservoir and battery. That’s roughly the size of a few stacked coins. It holds 200 units of insulin, which is less than the t:slim X2’s 300 units, so you’ll refill it more often.
Unlike the t:slim X2, the Mobi has no screen. You control it entirely through a mobile app on a compatible iPhone. A physical button on the pump itself lets you deliver a bolus without your phone if needed. You can wear the Mobi clipped to clothing, tucked in a pocket, or stuck directly to your skin using an adhesive sleeve.
Automated Insulin Delivery With Control-IQ
The feature that draws most people to Tandem pumps is Control-IQ technology. This software reads glucose data from a paired CGM sensor and automatically increases, decreases, or suspends your background (basal) insulin delivery to keep blood sugar in range. It can also deliver small automatic correction doses of insulin when glucose is trending high. The system targets a glucose range it sets internally, which you cannot change, though you can customize your basal rates, insulin-to-carb ratios, and correction factors.
This makes it what’s called a “hybrid closed-loop” system. It handles the background adjustments automatically, but you still need to enter carbohydrate counts and confirm meal boluses yourself. The “hybrid” label reflects that mix of automation and manual input.
Predictive Low Glucose Suspend
Tandem pumps also offer a feature called Basal-IQ, which focuses specifically on preventing low blood sugar. When the system predicts your glucose will drop below approximately 85 mg/dL within the next 30 minutes, it suspends insulin delivery automatically. Once glucose levels start recovering, delivery resumes. This is particularly useful overnight, when lows can happen while you’re asleep and unable to respond.
Compatible Glucose Sensors
Tandem pumps don’t measure glucose on their own. They rely on a separate CGM sensor worn on the body that sends readings wirelessly to the pump. Currently, Tandem pumps work with specific versions of the Dexcom G7, all versions of the Dexcom G6, and the FreeStyle Libre 3 Plus sensor (t:slim X2 only). The choice of sensor matters because the automated insulin adjustments depend entirely on receiving accurate, continuous glucose data.
Infusion Set Options
The infusion set is the physical connection between the pump and your body. Tandem offers several types to accommodate different body types and preferences:
- AutoSoft 90: A flexible cannula inserted straight in at 90 degrees, with an automatic inserter.
- AutoSoft XC: Also 90 degrees, but with a larger grip that makes disconnecting and reconnecting easier.
- AutoSoft 30: A flexible cannula inserted at a 30-degree angle, better for leaner body types with less subcutaneous fat.
- VariSoft: Lets you customize the insertion angle, with two cannula length options.
- TruSteel: Uses a steel needle instead of a flexible plastic cannula, with extra adhesive for better staying power.
Most people start with one of the AutoSoft options and switch if they run into issues with absorption or comfort at their infusion sites.
Mobile App and Data Sharing
The t:connect mobile app pairs with the t:slim X2 over Bluetooth and serves two main purposes. First, it acts as a secondary display, showing your pump data and CGM readings on your phone and relaying alerts. Second, it can upload pump and CGM data wirelessly to the cloud so your healthcare team can review trends at your next appointment. With a compatible phone and the right software version, you can also deliver a bolus directly from the app without touching the pump itself.
Data uploads happen periodically rather than in real time, so the app isn’t meant for live remote monitoring by caregivers or doctors.
Software Updates Without Replacing Hardware
One practical advantage of Tandem pumps is the ability to receive software updates during the pump’s four-year warranty period. This means you can gain access to new features or algorithm improvements without buying a new device. For the t:slim X2, you connect the pump to a computer and log into your Tandem Source account. For the Mobi, updates happen through the mobile app. Some updates require completing additional training modules before they activate, and eligibility is limited to users whose pump is still under warranty.