#Fiasp two months on. Bedded in and settled down – what did I change to get there?

#Fiasp two months on. Bedded in and settled down
#Fiasp two months on. Bedded in and settled down

I’ve been using Fiasp now for two months, and as discussed in the various items I’ve written, the first month proved to be a fairly dramatic bedding in period, with all sorts of strange things going on, and it taking a while to get used to.

As a result of that first month, I made the following changes to my treatment regime:

  • ISF Adjustment
    • Normal Daytime adjusted from 2.8 to 2.4 mmol/u
    • Sensitive period adjusted from 4.8 to 4.2 mmol/u
    • Overall, approximately a 13%-14% reduction in insulin sensitivity
  • ICR Adjustment
    • Daytime ICR adjusted from 1u:10g to 1u to 9g
    • Sensitive period ICR adjusted from 1u:12g to 1u:10g
    • Overall, about a 10%-15% increase in insulin required to cover the same amount of carbs
  • DIA
    • Original DIA on NovoRapid was 4 hrs
    • Initial DIA with Fiasp was 2 hrs
    • Current DIA with Fiasp is 3 hrs
  • Site life
    • Site life now has a maximum of three days, but between two and three days is more frequent
    • If I notice pain at a site, I need to change it immediately, otherwise I notice unexplained high glucose levels. This happens more frequently than it did with Novorapid
  • Insulin in reservoir
    • Once the insulin has been in the reservoir beyond three and a half days I see a drop off in efficiency. As a result, I load the reservoirs with less insulin so that I am changing them out every three days.

As you can see, with the Fiasp, I seem to be less insulin sensitive compared to the Novorapid I had previously used and I’ve found more variables that make it appear less stable. It does, however, continue to work really fast.

The Hba1C I took away from my hospital appointment on 8th May was 5.5% (37mmol/mol) which is non-diabetic, and coincided with the use of Fiasp and oref1, the newer algorithm on OpenAPS (which I find works very well with the Fiasp).

The stats above for the last month look okay, but are a little unreliable as they include rather a lot of compression lows when asleep over the past two weeks caused by using a slightly different sensor location that has skewed the low data rather. Whilst there are a few highs, they aren’t THAT high, with an average of 12mmol/l!

Aside from the above, there are also other lessons that I’ve learned in using Fiasp with oref1. These are more directly related to using an advanced closed loop algorithm and are not likely to affect a wider user population. These include:

  • Low and medium carb meals don’t really need bolusing. If I announce the meal and a carb estimate (a button on my phone) then oref1 with Fiasp handles it with no issues (that’s essentially up to 60g of low GI carbs).
  • Multi-course or buffet-type browsing meals can be handled similarly to the above, with the addition of a rough bolus that will cover any fast acting carbs in the meal.
  • Meals with higher amounts of carbs and fast acting carbs, I need to bolus the full amount up front as oref1 can’t keep up with the absorption, even with Fiasp, but it does seem to work really well at avoiding both spikes and lows.
  • If I don’t bolus the full amount for something with more carbs, further Fiasp top-ups are less effective at lowering a continuously rising glucose level. I suspect that this is due to the administration of a large dose and the added B3 in the location. I am unable to prove this though.

So the question I’ve been asked a few times is “Will I continue to use it?”. Given the learning experience so far, I think so. I’ve achieved some of the smoothest lines with the tweaks in the closed loop and as long as I’m aware of the physical limitations I’ve run into, and work within them, then I get good results.

The changes that I needed to make seem to have remained stable for more than a month, so for now, I’m keeping going with what’s in place using Fiasp. It, combined with oref1, has resulted in some of my lowest Hba1C results that I’ve achieved, without extreme hypo issues and whilst eating a fairly normal diet.

As always, if you’ve been using Fiasp, please fill in this form to let others know what you’ve found, and of course, other people also use Fiasp, and they’ve shared their experiences. Those can be found here. The more people that complete the form, the better the picture we have of user experiences, so please go ahead and share!

For me, it seems that, even with all the caveats that I’ve noted, it works very well as an insulin for looping!


  1. Hey great feedback, slightly personal but I was just wondering id you’d noticed any change/gain in weight linked to the increased insulin levels needed?

    • No, but I wouldn’t expect to see it linked to a change in insulin needed.

      I’d expect to see it if I was eating more though (and since Christmas, I’ve hardly been an angel on the eating front…).

  2. Do you fill the reservoir with insulin from the fridge? I learnt to keep an open vial at room temperature and use it from there (easier to fill the reservoir without bubbles too).
    I’m trying to understand what could be the factor that leads to Fiasp being less effective after being in a reservoir for 3 days vs. being in a vial at room tepmerature …

    • I fill from the fridge, yes – and don’t have air bubble issues.

      To be honest, I wouldn’t want to leave the vial at room temperature for 2.5 weeks (I’ve never done that with any fast acting insulin, as up until Fiasp I used penfills).

  3. Interesting stuff. I’m not sure it’s room temperature or the reservoir that is the problem, but the tubing. I find I can keep it in my reservoir for a week but I need to change the tubing every 3 days maximum or it will not work as well.

    • I suspect that it’s me losing on the pump at night and warming it too much. Novorapid used to cope with that for six days. Fiasp not so much…

      • Why did you needed more insulin for meals and corrections? I thought this at first but it was because I wasn’t pre-bolusing. I was having too many lows and changed everything back to the same ratios I had using NovoRapid. I do find I can’t “superbolus” with Fiasp as I will have highs later on from the shorter tail, but don’t need to as much as long as I pre-bolus with it.

        • My sensitivity changed. I don’t need to Pre-bolus (at eating time seems to match my absorption pretty well) but I do need more of it for the same effect. Some of that was caught up in the issues I described with sets and reservoirs, but once I’d got those stabilised, I simply need more and I think that’s down to the b3 it’s combined with.

  4. Does the shorter activity half-life of Fiasp and its use in the context of an APS mean that those top-ups in cases where you’ve missed the boat a bit with early carbs might be effectively combatted with something like Afrezza?

    • I think you’d still have to be careful. The tail still runs out quite a long way and although what I call the “effective” tail due to lower insulin amounts remaining is lower, I think it could still catch you out.

  5. Is there any hint how Fiasp compares to Humalog? From what I have seen all comparisons are Novorapid vs. Fiasp. I currently use Humalog with pump and CGM. Is it worth switching to Fiasp?

    • There are one or two Humalog users on Twitter who may be able to answer that question. The posts of theirs that I’ve seen suggest a similar difference, but it really depends on how Humalog affects you and when it kicks in. It’s probably worth a try in order to find out.

    • I just switched to Fiasp from Humolog (insurance chose for me). I’m on Medtronic 670g closed loop. Every morning I would wake up at 118 to 120 while using Humolog. Even after later and/or higher fat dinners. Fiasp is running me at 150. You can’t forget to pre-meal bolus with Fiasp. It takes forever to recover. I had a large glass of wine one evening and could not get below 200 until about 7am. So far I have been using a lot more insulin and changing infusion sites every two days.

  6. I was wondering if you had thought about mixing the Fiasp with Novorapid or Humalog insulin? While this hasn’t been tested, perhaps this could get you faster-acting insulin without as much of the drawback of the decreased insulin sensitivity? I’m not well-versed as to what effects the mixing of the two formulas could have, but it may work? I was thinking about trying this out.

    • I’m aware of people using this approach. My issue is having enough NovoRapid to be able to try it out.

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