Fiasp - considering switching to Fiasp

Hi all,

There are a few threads on Fiasp (they are old threads -so I’m unsure if still relevant, maybe some users have stopped using Fiasp)

I’m considering switching from Novolog to Fiasp because Fiasp is supposed to start working faster. I’ve read about Fiasp allergies.

Please share your experiences if you feel that Fiasp has been faster than the other bolus insulin, and if you disagree.


My son tried it. Did a few tests, acted the same as Humalog in him. Stung when injecting. Went back to Humalog.

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I did not see much speed difference. But others think it works much faster for them.

NovoLog and Humalog work pretty fast for me, so that might be why I did not notice much difference.

The best way to know how it will work for you is to try it yourself. You don’t have to switch all the way without trying it. Just get a few vials and try them first. And then decide if you want to switch.

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I tried it for a bit - initially it seemed to work really fast but that effect wore off. It was just as easy to use my regular stuff, plus Fiasp isn’t really approved to use in pumps, FWIW.


I made the switch from Humalog to Fiasp a few years ago while on MDI and found Fiasp to be noticeably faster. Pre bolus times for most meals are about 5-10 minutes max. I also found the tail end to be quicker which can cause highs for large or slow digesting meals. Now I use Fiasp in Omnipod and use a minimal pre bolus time and almost always extend about 10-20% of the bolus for 1/2 hour which seems to fit pretty well. No allergy for me. I have had occasional mild stinging with a large bolus.

Fiasp has a copay discount card online in case you decide to try it.


I switched from novolog to fiasp, and have seen a general trend that fiasp is quicker in onset for me. This makes a big difference for me since my schedule isn’t always predictable, and I don’t always have a lot of heads up before eating to prebolus way in advance. I still do need to prebolus with fiasp, but that prebolus time generally is shorter than with novolog, for me.

Sometimes fiasp stings if I take a big bolus with it, but nothing too bad IMO. I have heard from some users that they feel like there are more occlusions in pumping occur with fiasp than with novolog/humalog, but that hasn’t been my experience so much.

Everyone is allowed their own preferences, and I think it’s definitely worth it to fiasp to see if you like it better or not! Some CDEs and endos carry samples so that may be worth it to ask. I don’t see any harm in getting a vial/pen or two to test it out since being comfortable and confident in our tools is an important aspect of managing diabetes :slight_smile:


I’ve tried it twice, about 6 months apart, in a pump. As others report above, I did not find it faster enough to make any difference in life (it shaved 5 minutes off a 20- to 30-minute wait time), it stung occasionally (but so did Lantus from time to time), it left red welts at infusion sites. And I had haywire BGs. I went back to Humalog both times.

But some people love it, so give it a try and see if it works for you.


Do you use a pump?
If there is a sting, resulting from a large bolus, how many units is a large bolus?


Yes, I use the tandem t-slim x2. I have used the medtronic 670g with fiasp as well.

Eh, for me I’d consider a large bolus more than 3u, and I’d say I get a sting from a large bolus maybe 1/20 times? It’s not that common and it’s probably a pain 2/10 on the pain scale I’d say.


I have been using Fiasp in an Omnipod since April 2017, which is almost 3 years. Wow! Time flies.

I found it worked better than Humalog. It is a lot faster acting for me and continues to be fast. I used to inject humalog like 45 minutes before a meal. With Fiasp it is more like 15 minutes early.

I have never compared to novolog/novorapid so I have no idea how they compare.

I get no stinging on injections. My pump sites are fine. I have no reason to stop using it.


Everyone’s experience is so different!

Thank you -everyone.


I tried Fiasp for several months, hoping it would eliminate the welts I was getting with Humalog in Omnipods. It did, but I didn’t experience it working any faster than Humalog. Worse, for me, my body required increasingly more insulin for boluses, as much as 4 times. It’s like I was injecting saline. I switched back to Humalog and boluses have returned to normal.