When Medtronic was going to stop selling supplies for my Animas insulin pump, I had a choice to either switch to a Medtronic, Omnipod or a Tandem pump. Having used Medtronic and Omnipod for a couple of years prior, and a Tandem t:slim X2 on a Clinical Trial, I decided to go with the Tandem pump which now comes with Basal IQ technology. What that means is that the insulin pump suspends insulin delivery if the predicted glucose reading 30 minutes ahead of time is below 80mg/dl. This also means you need a Dexcom G6 CGM for this to work.

Overall I’d give the pump a 7/10 mainly due to the lack thereof service from the manufacturer and the cumbersome order process.

CategoryMedical Device, Type 1 Diabetes
Likes+ Small Form factor
+ Rechargeable battery
+ Update-able Software
Dislikes– Order process
– Customer support
– Certain features
Where to Buy (US) Tandem Diabetes


The pump and supplies were shipped via UPS. Although the outer shipping box as well as the Cartridge and Infusion set boxes were fine, the pump box looked badly dinged (as you can see in the picture below). And the pump itself was not anchored to the box (and was just sitting in the flimsy cut-out) due to poor packaging design. That combined with the fact that the pump screen did not have a protective film (which almost all touchscreen devices do, including a laser tape measure I recently bought), made me think they probably sent me a used pump. So I went online to see if someone made an unboxing video and stumbled upon Diabetic Danica’s video and  calmed down after I saw that hers didn’t come with one either. 

The order form that came in the box listed the Cartridge, Infusion Set, and Pump and I knew the t:slim had a different cartridge design than the Animas/Medtronic pumps so I was a little paranoid when I didn’t see a Syringe/Needle box on the list. Don’t fret, they’re in the Cartridge box.

Tandem tslim X2 insulin pump with Basal IQ: What's inside the box
What’s in the box

The number of Cartridge and Infusion set boxes may vary depending on your insurance coverage. My box came with the following. 

  1. Tandem t:slim X2 insulin pump loaded with Basal IQ software (1)
  2. TruSteel, 8mm/32″ Infusion set (2): This is the same as the Animas Contact Detach but it has the new Tandem proprietary t:lock connector instead of the luer-lock (old versions of the TruSteel had luer-lock). Also if you’re curious about the tubing length, it is measured from the cannula (where it inserts into your body) all the way to the connector.
  3. VariSoft, 13mm/23″Infusion set (2): This is the same as the Animas Comfort Short but it has a Tandem proprietary t:lock connector instead of the luer-lock.
  4. Cartridge box (4): Each box has ten 3ml cartridges with t:lock connector, 10 needles, and 10 syringes. 
  5. USB Charger Cable (1): You can plug this into your Computer or Car USB ports.
  6. Wall Charger (1)
  7. Black rectangles on a key-ring (2): These are for removing the cartridge from the pump. You could alternatively use a coin (I use the used connector) to wedge it between the pump and the cartridge to push it out during cartridge change.
  8. Pump Case with removable clip (1) 
  9. Pump user guide
  10. t:connect user guide


There are plenty of blog posts as well as videos on the Tandem X2 pump itself, so I’ll focus on the Good, Bad, and In-between in this article.

The Good:

  1. It is integrated with Dexcom G6 and suspends insulin delivery during predicted BG lows (Basal IQ). When insulin delivery is suspended, it appears as a vertical red line on the CGM graph on the home screen.
  2. Re-chargeable battery wins every time. I used to hate replacing the battery on my Animas pump. You can charge the pump while you’re still connected (which I usually do when I’m on my computer). Bolus delivery is NOT interrupted during charging. My pump lasts about 4 days (25% battery) on a full charge.
  3. The pump has a small form factor and has a sleek and stylish feel.
  4. The Touchscreen is nice. 
  5. Keypad entry for pretty much any user input is awesome. I had finger fatigue from pressing buttons on my previous two pumps.
  6. Temp basal rates can be set up to the minute as opposed to 30min increments. Also, the temp rates can pretty much be any numerical % as opposed to 10% increments (or decrements) with Animas. The temp rate is gated by the minimum allowable rate determined by your regular basal rate at a particular time. There is a separate option called “Stop Insulin” to suspend insulin delivery.
  7. The Home screen has pretty much all the info you need: Date, Time, Remaining Battery %, Remaining Cartridge units, Basal IQ state, Dexcom G6 graph, Dexcom G6 BG numerical value, Insulin on Board and Time remaining, Basal/Temp state, as well as the Status screen which can be accessed by tapping the Cartridge indicator (not-so-obvious).
  8. The screen auto-locks pretty much after you complete a specific task/interaction like bolus delivery, basal adjustment etc.. so you don’t accidentally cancel a bolus delivery or temp rate for instance which is really nice.
  9. The Cartridge capacity is large holding 300 units! (compare that to 200 units on the Animas). 
  10. Due to the Cartridge design, you don’t get back pressure if your pump is in the front pocket of your pants when bending, kneeling and hence no more of the ‘Pump is not primed. No delivery’ alerts like with the Animas
  11. The pump case seems well made with air and pressure vents. You can also do a cartridge change without removing the case. Also, the pump clip is removable from the case and the case can be used independently. I can’t comment on the longevity of the clip at the moment as I’m using mine without. But from what I’ve read on other blogs so far, the clips don’t last very long. 

The Bad:

  1. The Pump box packaging is terrible and cheaply made with what looks like low-weight cardstock. What good is a pump if it arrives damaged?
  2. Dexcom G6 reception on the pump is very very poor. The user guide claims it to be 20ft. I’m a cyclist and ride pretty much everyday. A cycling jersey has 3 (sometimes 2) back pockets one of which I use to hold my pump. If the pump is on the opposite side of my jersey, there is no BG reading on my pump. I go on long rides (30+ miles) and although I set a Temp rate on long rides, I was excited with the Basal IQ feature to prevent lows while riding but the Basal IQ doesn’t work if there’s a signal loss – which means I have to stop and check my BG on my phone every couple of minutes. Also, the other night, I noticed that if your pump is on the side opposite from the Dexcom G6 sensor while sleeping, you don’t get any readings on the pump. This is a pretty basic not to mention super important feature that Tandem Diabetes should have gotten right. 
Dexcom signal comparison with respect to tandem pump location
Dexcom signal comparison with respect to pump location
  1. There is an AUTO OFF setting on the pump which shuts off insulin delivery if you don’t interact with the pump for a set time. I don’t remember if it came turned off or I mistakenly turned it on. Mine was set to turn off at 12 hrs. I was woken up to an alarm one morning and didn’t know why it wanted to turn off insulin. That’s when I called Tandem tech support and found out you could turn it off manually. Upon asking why this feature was even available on an Insulin Pump meant to deliver insulin for patients who don’t produce insulin on their own, the rep said when they did user studies they found out that some patients may need this feature to prevent LOWs based on talks with their endocrinologists. Btw, isn’t the Basal IQ feature supposed to prevent LOWs in the first place? Also, in my 17 years of being a T1D and having seen many Endos, the need to shut off insulin for lack of interaction with a pump has never been brought up or discussed. If you find yourself in a similar situation and want to turn the feature off, you can find the setting under My Pump>Alert Settings>Pump Alerts>Auto-Off. At least the good thing is it gives you an alert with audio (even if you have your alerts set to “vibrate”) if you have the feature turned on.
Auto off feature on Tandem tslim pump
Tandem tslim insulin pump and Dexcom signal
  1. Now, the million dollar question – Does Basal IQ work?? I’ve had mixed experiences with it as it seems iffy at times. I woke up one morning ~5AM to 82 mg/dl as I was feeling a little jittery to find out that the pump hadn’t suspended basal rate. So I had to set a temp rate for 45 min and drank some juice to bring it to the 100s. On a different day, it suspended too much with led to BG spike after a couple of hours. Another time, it suspended for no good reason as my BG looked like it was well close to 150 mg/dl which led to a spike later. 
Basal suspend when BG was normal leading to spike later
BG spike after Basal suspend when BG was in normal range
  1. The minimum tubing “fill/priming” amount is 10 units. Although the ‘Stop’ button is available to press anytime during the tubing fill, it gives you a message that you can’t stop until you hit the unit minimum – which seems like a bug. Also, if you accidentally exit out of the “Cartridge change” process by pressing one of the buttons after filling the tubing, it’ll make you re-start the fill process hence wasting 10 units of precious insulin.  
  2. The HIGH and LOW BG alert have to be independently acknowledged on the Dexcom receiver (or phone App) and the Tandem pump. Acknowledging the alert on one device does NOT dismiss the alert on the other. So if you’re in the middle of something (like I usually am) and cannot get to both devices, be ready to hear a series of annoying beeps.
  3. If your Dexcom G6 transmitter is at its end of life and you need to change it, you have to independently do it on the Dexcom phone App (or Receiver) as well as the pump. I didn’t know this and I only changed it on my phone thinking it’d sync. 4 hrs later after phone calls to Tandem Tech support, I learned that although the previous sensor session expired, you still have to ‘Stop Sensor’ on the Tandem pump after which the transmitter ID field under Options>My CGM>CGM Settings will be editable. You then press ‘ Start Sensor’ on the pump and choose ‘Skip’ since you previously started the session on your Dexcom phone App. After ~5min, the CGM readings will start showing on the pump. In contrast, for a sensor change, you just do that thru your Dexcom App/Receiver and the pump will sync without needing any additional input.
  4. The button graphics as well as screens that seem to have a background gradient are pixelated which looks bad for a device that’s been on the market for so long. If this is purely software dependent, seems like it could have been fixed with any of the numerous software updates that have been rolled out in the past.
  5. No one ever answers the phone (be it Tech support or Billing) in the numerous times I’ve called Tandem which is really frustrating. The phone call directly plays a recorded ‘You don’t have to wait on the line to talk to someone, leave your number and someone will callback’ type message even after sometimes waiting up to 1hr! (10/22 Update: Someone in Tech support actually answered my call today!)
  6.  I’ve had 2 instances of Cartridge failure possibly due to insulin leakage in the membrane (with no alarms, just BGs in the 500s) in 3 months of use – see the ‘In-between’ section for more on the Cartridge design.

The In-Between

  1. The ‘Load Cartridge’ option is not visible on the screen when you go to Options. So you need to scroll down to access it. It’d have been nice to have this available upfront as this is one menu item that gets accessed a lot!
  2. There seems to be a bug in the ‘Screen Lock’ setting. I have mine set to lock after 60 seconds but mine locks up way sooner than that, sometimes after 5 seconds. The screen lock should be dependent on the “idle” time and not when you’re interacting with it which is what happens in my case.
  3. The Screen/Display Brightness cannot be adjusted so its super bright in the dark. If you’re like me, you can use it as a night light to go to the bathroom!
  4. The Cartridge is designed with a inflatable membrane/bag (if you will) which inflates as you fill with insulin. This makes it impossible to visually check for air bubbles in the membrane. Although they have instructions on how to get the air bubbles out via the fill syringe, it’s not a 100% fool-proof and I do still see air bubbles in the tubing on every cartridge change. 
Tandem Cartridge
Tandem Cartridge
  1. Speaking of Cartridge design, since the syringe and cartridge are not integrated, there’s more medical waste to throw away.
  2. The Cartridge/Infusion set change process takes me at least 11-12 minutes due to the super slow cartridge priming.
  3. You cannot set a Duration on the ‘Stop Insulin’ feature which is annoying when you can’t set a Temp rate low enough and suspending insulin seems like a better bet.
  4. Although the pump is watertight to a depth of 3 feet for up to 30 minutes, it is NOT waterproof. So you can’t swim, scuba dive, or go surfing with it. You may be able to shower with it which I haven’t tested. If you plan to, do it at your own risk.
  5. Aesthetically speaking, I’m not fond of the Chrome border around the pump screen – I feel it makes it look cheap.


With the limited insulin pump options on the market in 2019, the Tandem X2 with Basal IQ pump seems like a decent choice although I’m holding out for the unicorn in the near future.

Disclaimer: The views expressed on this website are solely those of the authors and are here to help people make an informed choice before a purchase. The authors or the blog itself does not get any compensation from the product manufacturer or third-party websites/vendor links that are posted here.

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