I started using the Tandem t:slim X2 insulin pump on December 13 and this review is long overdue. After 2 months, I am mostly happy with the pump. I am comfortable navigating through the menus and have learned a few shortcuts. I like the touchscreen and the “modern” look of the pump. I like knowing that I will be able to add new features to my pump with software updates. At the same time I am annoyed with almost daily alerts about one thing or another. Most significantly, I am frustrated with occlusion alarms which I never experienced with previous pumps.
The Good Things
I like the touchscreen and being able to enter numbers for carbs and BG levels rather than scrolling up and down.
I like the looks and size of the X2.
I like the ability to turn off the screen to preserve battery life. I like the ability to go backwards through menus and tap the “T” to return to the home screen.
I like being able to fine tune settings. For example with Active Insulin Time, my early Medtronic pumps restricted changes to hours. 3 hours seemed too short; 4 hours seemed too long. Then with Animas, I could select 3-1/2 hours or 4 hours and neither seemed perfect. Now with Tandem, I am using 3-3/4 hours and could even select 3 hours and 39 minutes.
I like the ease of setting Site Reminders on my X2. This wasn’t a feature that I particularly missed on previous pumps, but now that I have it, I use it often.
I like that the reservoir icon remains red after I clear the customizable low reservoir alert.
I like that I can read the pump screen in bright sunlight when hiking. Sometimes I have to take off my sunglasses to read it, but it is much better than my Animas pump screens which were totally unreadable.
I like that Tandem has attempted to create a pump that is contemporary and has worked to creatively meet the needs of insulin users.
I like that I will be able to download software updates to add new features such as CGM integration to my X2 as they are released by Tandem. My fingers are crossed that these updates will be allowed under Medicare rules.
I really like this pump.

The Annoying Things
I find filling the reservoir to be an overly complex and time-consuming process. It is like a “black hole” because I can’t see the insulin in the reservoir or troubleshoot air bubbles. I dislike that the icon on the home screen does not give me a more exact estimate for the number of remaining units of insulin. I can start with a syringe of 250 units and the pump registers 180+ units. After delivering 10 units of insulin (that’s half a day for me), it displays units of insulin rounding to the nearest 5 units. Below 40 units it begins to show specific units. I seem to “lose” more than the 45 (!) units that Tandem indicates as normal.
There are alerts which interrupt me on almost a daily basis. I use temp basals of “0” often for 30-60 minutes when I am moderately low and don’t want to eat. Unfortunately the X2 alerts 2 minutes later to indicate that my basal rate is less than half of my normal basal rate. Well, duh! That’s what I programmed. I suspect the alert is actually a result of a sensor, but IMO software should dismiss the alert if the basal change had been programmed.
I dislike the pigtail connection between the cartridge and the tubing. It tends to stick out and cause tubing to hang out of my clothes.
The t:clip vertical case that accompanies the X2 is bulky and poorly balanced. My guess is that it was designed by men who wear it on a belt. When I clip it to my waistband, the pump is top-heavy and leans forward resulting in an odd bulge in my clothing. If I bend over, it frequently falls off. Rumor is that a new case will be released soon.
Things to Which I am Indifferent
I have never wanted a rechargeable pump but it doesn’t bother me. The X2 charges quickly and does not require a proprietary charger. I can even charge it in my car. So it’s fine.
A lot of people like the way that basal and bolus settings are programmed together in blocks of time on the t:slim. So far I don’t find much benefit doing it that way but I don’t care.
The X2 holds 300 units of insulin. I was fine with 180-200 unit reservoirs, but it’s easy to fill the cartridge partway.
User Error Problems
Some of my issues with the X2 have been due to “user error” and are resolving as I become used to the differences between the X2 and my previous pumps.
The most common error that I make is not resuming insulin after filling the cannula on new infusion sets. I can’t quite remember how it was handled with Animas, but I never had the problem of not resuming insulin. With the X2 I have to wade through a couple of screens like “Stopping Fill” and “Test BG in 1-2 hours” before I get to the option of “Resume Insulin.” Many times I have returned the pump to my pocket before those extra screens. Thankfully I always get an alarm that the pump is not delivering insulin and can fix the problem. I am getting better at slowing down and not forgetting to resume insulin, but occasionally I still mess up.
Another annoyance is if I accidentally touch Bolus on the home screen (and this is easy to do) and don’t clear it, I will get an alert for an incomplete bolus although I haven’t entered any data. The alert will not clear until I go back into the pump, clear the alert, and back out of the bolus feature. Once again this is happening less often as I become more focused when handling the pump with an active screen and being sure to push the top button to turn off the display.
I used Animas pumps for the last 4 years and bolus insulin is infused quickly and immediately. Tandem pumps use a patented “Micro-Delivery” process and can take a couple of minutes to infuse a bolus. More than once I have pulled the same trick that used to mess me up with Medtronic pumps. I bolus for my breakfast while getting dressed. Forgetting that I programmed a bolus a minute ago, I unhook my pump to thread the tubing through the hole in my pocket or even to take a shower. Meanwhile insulin is dripping out and I have no way of knowing how much of my bolus I missed. Once again I am working hard to break this habit.
Occlusion Alarms – The Elephant in the Room
I have used an insulin pump since 2005, first Medtronic and then Animas. In all of that time I had at most 2 or 3 occlusion alarms. If you want to add “loss of prime” alerts on my Animas Ping, maybe you could add 5 more alarms. In 12 years I estimate that I had a problem with insulin delivery 7-8 times. Less than once a year. I cracked pump cases more times than I can count, but I never had a pump replaced because it did not deliver insulin.
I have used the Tandem t:slim X2 for almost 10 weeks. In that time I have had 9 occlusion alarms resulting in an immediate stoppage of insulin delivery. The first couple of times I panicked at the shrieking pump alarm fearing that something was actually wrong. Nope. Not once has there been a problem that did not disappear by working my way through the menu screens and pressing “Resume Insulin.” The vast majority of these alarms have been while delivering meal boluses, but not all.
Before I go any farther, I must admit that I do not change my cartridges every 3 days as recommended. (I do change infusion sets every 2-3 days.) My first occlusions happened when my cartridges had been in use for 8, 9, and 7 days. So I shortened my cartridge use and had occlusion alarms at cartridge ages of 2, 5, 7, and 1 day. I have only used one cartridge without an occlusion alarm. FYI my total daily insulin dose ranges from 13 units to 26 units and averages 18-20 units. I regularly used reservoirs for 8 days with both Medtronic and Animas and never had a problem.
I have been in contact with both people at Tandem and “experts” in the diabetes online community and have considered every suggestion. I have changed cartridges more frequently. I have used a Spibelt and a Flipbelt. I have used the awkward Tandem case because Tandem techs think it is a temperature issue. (I did learn that the case traps in heat and your insulin goes bad in about 5 days.) I have carried the pump in my pocket and worn it on my waistband. I am 100% convinced that my manually inserted Comfort Shorts (Silhouettes) are not the problem. The occlusion alarms have not correlated with site age and have randomly occurred at site ages of 1, 2, and 3 days. I have had no failed or kinked sites and have used these sets for 12 years with no issues. A Tandem tech assured me that the pigtail design of the cartridge/tubing is not at fault because an internal coil protects it from kinking.
Replacing the pump has not yet been requested by me or suggested by anyone at Tandem. I am currently wearing the pump on my waistband using a Nite Ize hip clip attached directly to the pump and I will see if I can make it 2 weeks without an occlusion alarm. (Thanks Sarah Sugabetic and Kerri Sparling.) My record is 13 days; so far I’m on Day 6.
One thing I must give kudos to Tandem on is that when I get an occlusion alarm during a bolus, it does let me know how much of the bolus was delivered so that I can reprogram the rest after clearing the alarm.
Everyone at Tandem has been respectful and concerned. I sit here in the middle of this experience wondering “What separates the many people who never have occlusion alarms from those of us who are plagued with them?” For me these alarms are #FakeNews and #AlternativeFacts and not once have I seen a kink in my tubing or needed to change out an infusion set or cartridge to resolve the issue.
Conclusion
I like my X2 and do not regret the purchase. I wrote extensively about why I chose this pump and I would not make a different decision today.
At the same time I am conflicted about wholeheartedly recommending this pump to others. How can I recommend a pump that averages a once-a-week stoppage of insulin for seemingly no reason? I admit that I don’t follow all of the rules, but in general I am a conscientious PWD and am doing nothing differently than I did with Medtronic and Animas. Because I have always heard the occlusion alarms, I have been able to restart insulin delivery immediately and have suffered no ill effects from these events.
I delayed writing this pump review because of the occlusion alarms. My hope has been that every “fix” would resolve the issue and I could write a glowingly positive review of the X2. I want to love this pump and I want Tandem to grow and be a successful pump company. As I said before, I really like this pump.
Maybe the hip clip will be the solution.
If not, I will probably argue for a replacement pump as the next step. At this point I am confident that I will not be abandoned by Tandem.
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Please note that this review only reflects my personal experiences. Many users do not experience occlusion alarms with the t:slim X2. Others had these problems with other brands of pumps and don’t with Tandem. Be sure to talk with your medical team, contact a Tandem representative, and read as many reviews as possible if you are in the market for a new insulin pump.