FIASP for Insulin Pumps


My experience with Fiasp working well or not had to do with the speed the insulin was delivered. First I tried Fiasp in an Animas Vibe pump set to highest delivery speed possible and it was not successful, then I tried Fiasp in an OmniPod where you don´t have the choice to set the delivery speed yourself, but it´s comes with a r-e-a-l-l-y slow delivery speed set from the factory and the OmniPod works slike a charm with Fiasp. Could all of the issues we think has do to with infusions set rather be a problem connected to how fast the different pumps deliver insulin?


I have also wondered about that but it seems that the tSlim: X2 delivers pretty slowly. My previous Animas Vibe seemed to deliver insulin much faster than the X2. My issues do seem to stem after I have had a high carb (Mexican for example) meal where I’m doing around 15 units of insulin.

Regards, Steve Yarbrough


Thanks for the input! I did change my settings slightly but it didn’t seem to make a difference.


I appreciate your feedback! I think at this point I’ll keep with my humalog. It is a bummer that it works so great (when it does).


I know. That’s my feeling exactly. In the beginning I thought it was a miracle but then I started hitting the inconsistency of the site absorption issues. My insurance doesn’t cover Fiasp so I’m having to buy it from a Canadian Drug Store at $70/bottle so I’m thinking that I might also return to Humalog once my current supply runs out.

Regards, Steve Yarbrough


I’m using Fiasp on my semi-antique pager-style Minimed, and it also has factory-set s-l-o-o-o-o-o-o-w delivery, so maybe that’s why I haven’t had the problems some others have reported, specifically the sting, the red marks, no noticeable improvement over regular analog insulins etc. OTOH I do seem to experience a pretty noticeable fade, especially in the last 12 hours or so of a reservoir.

More recent Medtronic pumps DO have a setting to control delivery speed, which people may not be aware of. Worth checking that out, for anyone using Fiasp on a Mdt.


Same here, except I do see improvement over Humalog and I change my pod every 48 hours so I wouldn´t know about the last 12 hours of the reservoir as you mention. On the other hand, I´ve always changed my infusions sets and reservoir every 48 hours no matter what pump or what isulin I´ve used. Third day has always been a mess, so I just change to avoid problems.


On the cost of canada orders, if you get 9 at a time they are aroun.d $40 per vial. Which is a LOT cheaper.
The first few weeks were definitely better for me when I started fiasp.
But, I still feel like it is much better than Novolog was for me.


I us an animas pump and it’s set to normal speed and have no problems at all.


That´s great! When I used Fiasp in my Animas Vibe the pump was set to the highest possible delivery rate.


New here and this is my first post, but sharing the experience I’ve had using FIASP on the Tandem pump over the last 5 months -

  1. I haven’t experienced any stinging or significant site irritation with FIASP. I attribute this to the slow deliver speed. I Had stinging quite often on my previous Animas and Desitronic pumps with any insulin - and that was because delivery was so fast,

  2. for the first 4 months I had no problems - and loved the faster action from FIASP. Like others I need a second bolus to cover fats and proteins.

  3. The fifth month I started seeing what appeared to be zero effectiveness. No matter how much I bolused at meal time or as a correction, sugars would continue going up. This has occurred four times now. Each time I confirmed the pump was working by disconnecting at the infusion site, initiating a bolus and making sure insulin was flowing. I reconnected - still no impact. Next I changed the infusion site. Still no luck. Finally I changed the cartridge and all was well again. I noted that the problem only occurred when I had less than 30u left in the cartridge.

I talked to Tandem and they said the pump wasn’t qualified yet with FIASP, but that other customers on FIASP were changing cartridges with 50u left to avoid problems. A waste of insulin for sure, but if it will let me continue using FIASP I’ll live with it.

Just to confirm this is the issue, I’m switching back to Humalog to see if the problem disappears, I’m on the first cartridge so no results yet. I’ll have to do it several times before I’m satisfied.

For me the strange thing is why did I have no problems at all for 4 months, and what’s the explanation for the phenomenon? Tandem didn’t have an answer.


Paytone, welcome to Tudiabetes! I can definitely relate to your experience. I’m also a Tandem t:slim X2 pump user and I think the issue with loss of effectiveness is more due to how long you have been on the infusion set and less about how much is left in the cartridge. In my case, with the AutoSoft 90 Infusion sets I had been using, I could barely go 2 days before I started having reduced effectiveness. My doctor suggested switching away from the plastic canula to the TruSteel Infusion Sets. I made that change and have far fewer issues with losing site effectiveness. At first, I didn’t like the “two part” attachment of the TruSteel Infusion Set but as I have used it more, I actually like having an anchor “patch” stuck to my stomach for times when I loose grip on the pump… It doesn’t “yank” at the actual infusion site.

When the effectiveness would go away on the Autosoft 90, sometimes it would be gradual and other times I could do a large bolus and it would have almost zero impact. At that point, I would have to change the infusion set no matter how many days I had been on it and things would immediately turn to normal.

It really is frustrating because, when Fiasp works, it is far better than Humalog - hands down. It’s just the inconsistency that is really hard to deal with. I have very good control of my Diabetes. In the last 2 years all of my quarterly A1Cs have ranged from 5.4 to 5.9. I really don’t like the large swings that can happen when the loss of effectiveness hits… I have gotten up to a BG of 400 before finally resorting to giving myself a shot to bring it back down. I really never had to do that on Humalog.

Good luck!


Very odd. Do you have any ideas on this or are you absolutely baffled with no conjectures at all?

We have just started trying out Fiasp and are only on our second vial. Using it in our X2. Under the guidance of our Ped Endo but not in coordination at all with Tandem Customer Support.

So very interested in hearing Tandem/Fiasp experiences from others.

EDIT: Agreed that the Tandem t:slim X2 delivery rate is much slower than the Animas Ping even when the Ping was delivering at the slower of its two rates. We slow down the rate even further for bolus over 4 or 5 units by extending over 15 or 20 minutes.


Thanks for sharing this! I’ve been on FIASP about 3 months and love it, but I feel like I may be experiencing the same issues, will monitor more closely now.


Thanks for the feedback. Changing the infusion site didn’t relieve the problem for me, but I’ll try the infusion set you suggested and see what happens. Based on your description of how it works, I’m not as concerned as I was previously. I was wary of going back to stainless steel. Which cannula length are you using? I’ll share my results.

Great A1c track record! Congrats.

Have you tried Afrezza for knocking down signifcant high blood sugars? It works really well for me. If I’m at say, 350, and I use a 4unit cartridge, my BG starts dropping within a few minutes and and heads ‘double arrow down’ (If you’re using a Dexcom CGM) until I’m in range. After about 45 minutes it’s out of my system so I don’t have to worry about a ‘chasing the high’ crash hours after my correction bolus. FIASP stats working quickly, but doesn’t drop my blood sugar as quickly or clear my system as rapidly. I always drop an inhaler and a couple cartridges in my pocket when I’m out at a new restaurant or have a situation where I eat and then have no physical activity afterwards (dinner and movie for example). When I hit 300 and my BG is still going up I use it - never for routine use or small corrections.


The only theory I have is that perhaps there is still a small amount of air left in the cartridge and when the insulin level gets low the ratio of insulin/air gets so low the pump can’t deliver. Maybe FIASP is more viscous than Humalog so the pump has more problems? Shear speculation on my part. I haven’t changed the way I load the cartridge and after the first incident I was extra careful about pulling out air when filling the cartridge.


I’m using the longer length. Because of the “two part” attachment, you loose some of the length between the first adhesive patch and the infusion site patch. I have always used the shorter length in the past but tried some samples of the shorter length and they weren’t long enough. You might be able to get some TruSteel samples from your doctor. That is what I did. The cartridge doesn’t change… Only the Infusion set. My doctor did provide me both the infusion sets and cartridges and arranged it through the Tandem rep they work with.

The good part of the TruSteel infusion set is that there is no inserter. You just insert it by hand and it is painless. My doctor felt that the coating they use on the plastic canula to facilitate insertion may be a contributor to the loss of site effectiveness… Just a theory but moving to the steel needle seems to be benefiting me. I’m back to 3 days… Typically. I still encounter a problem with the site every now and then, but I have had that in the past with Humalog as well. It just seems that sometimes the site doesn’t work. I move things around to try to avoid this but sometimes it just happens.

Regards, Steve Yarbrough


I feel like people leaving in infusion sets too long may be contributing to loss of effectiveness of FIasp… Maybe it is just really sensitive to having a good infusion set. If you read the documentation that comes with all the steel infusion sets, they are only designed to be left in for 24-48 hours. Not three days. And yet I see many, many people talking about running metal infusion sets for three days… So if people are running metal infusion sets to three days, or running plastic infusion sets to four or five days, that could be contributing to the problem.

I have many issues with infusion set allergies (I have had numerous metal infusion sets get “no delivery” just because of my body’s allergic reaction to them), so it’s hard for me to objectively compare Fiasp to other insulins. I would say it’s a little more irritating, especially with large boluses. But I change my infusion sets out at the first signs of irritation, and so I have never experienced this issue of Fiasp inconsistency or working sometimes but not others. I do keep my cartridges in for as long as they last, usually two to six days depending on what I’m eating and if hormones are raging.

I also think delivery speed plays a role, as well as bolus size. I have much, much more success eating a low-carb diet with Fiasp becasue of hte small boluses. It’ll be interesting to see whether getting a new pump this fall (hopefully the t:slim X2) will allow for larger boluses delivered at a slower rate.


Interestingly there have been a few reports of problems with infusion sets/cartridges in the UK. If you find you have unexpected high numbers then check to make sure you have no insulin leaking from your tubing/cartridge connection.

Two days seems to be the best option for changing the cannula when using Fiasp for me.


I currently use Humalog (my endo doesn’t seem to be interested in different insulins) and the t:slim x2 and I will sometimes have loss of effectiveness when my cartridge gets down to 40-30u, and especially when it is below 10.