Fiasp, Lyumjev & Afrezza: Do You Still Need to Pre-Bolus? | T1D
"Neil, I use Fiasp, or Lyumjev, or Afrezza, do I even have to wait?" Great question, and this episode gets genuinely nerdy about the answer. Fiasp and Lyumjev are ultra-rapid analogs, built with ingredients (niacinamide in Fiasp, citrate...
The episode, word for word
Every single time I talk about pre-bolusing, somebody slides into my messages with, "Neil, I use Fiasp, or Lyumjev, or Afrezza, do I even have to wait?"
Great question. And the answer is a deeply satisfying "sort of, less, but kind of, it depends, please don't throw your phone." Let me explain, and let me do it for the 95% of us who are NOT on those, because this matters either way.
I'm Neil Greathouse, this is Your Best T1D Year.
So here's the landscape. Most of us, the big crowd, are on regular rapid-acting insulin. Humalog, Novolog, the standards we've been talking about all challenge. That's the 15-minutes-to-warm-up crew. That's most of you listening right now.
But there's a newer group of faster insulins, and this is where I want to get genuinely nerdy for a minute, because I did the homework and the science is actually cool. Fiasp and Lyumjev are what get called ultra-rapid analogs. Somebody took regular insulin and added ingredients to make it absorb faster. Fiasp has niacinamide, a form of vitamin B3. Lyumjev uses citrate and a tiny bit of something called treprostinil. Both speed up how fast the insulin moves out of the fat under your skin and into your blood. The fancy phrase is faster subcutaneous absorption. Faster absorption, faster onset.
Then there's Afrezza, which you inhale. The technical name is Technosphere insulin. You breathe it into your lungs, which have an enormous surface area, so it hits ridiculously fast. Its Tmax, the time to peak concentration, is about 12 to 15 minutes, and it delivers more than half of its glucose-lowering effect inside the very first hour. Your regular rapid insulin? It's done maybe 10% of its work in that same window. Ten percent versus more than fifty. And in a study literally called PRONTO-T1D, Lyumjev beat regular lispro on both after-meal glucose and time in range. So when I tell you the fast ones are fast, I am not eyeballing it. I read the pharmacology. There may be a quiz.
So if you're on the fast stuff, your head start is shorter. You might be dosing five minutes ahead instead of 15. That's a real perk, and if your after-meal numbers are rough and you're curious, that's a conversation worth having with your care team.
But, and here's the honest part, these faster insulins are still the minority. Most people aren't on them, for all kinds of real reasons, cost, insurance, access, what your doctor prescribes, what your body tolerates. So if you're sitting there with your trusty old Humalog, feeling like you brought a flip phone to an iPhone launch party, relax. The standard rapid insulins are excellent. Millions of us run gorgeous numbers on them. You're not behind. You just give yours a slightly longer head start, which is the whole skill we spent July building anyway.
Quick reality check while we're here. Fast insulin is a tool, not a personality. Nobody's blood sugar respects you more for being on the fancy stuff. The zero-to-sixty speed is fun, but a reliable Honda that starts every morning beats a Ferrari that lives at the mechanic. Reliability wins this race. Reliability has always won this race. It's like that old Mitch Hedberg line, an escalator can never break, it can only become stairs. Your trusty Humalog is the stairs. Always works. Never leaves you stranded on the second floor.
Your challenge this week. Just know your insulin. Pull up the name of what you take and look up, or ask your care team, roughly how fast it starts working. That one fact tells you how big your head start should be. Knowledge is the cheat code, and this one's free.
Want a simple one-pager on the common insulins and their timing? It's a free download at yourbestt1dyear.com. Sign up for the newsletter while you're there, follow the challenge, and join the roughly 1,500 people doing this together worldwide.
You're not doing a bad job, whatever's loaded in your pen or your pump. The fanciest insulin on earth still can't read your mind, and the most basic one works like an absolute charm when you time it right. Timing is the great equalizer. That's been the whole point since day one.
I'm Neil. Friday, the question to ask when you're pre-bolusing perfectly and STILL spiking. See you then.
This is the script as read on the mic, lightly tidied for reading. Education, not medical advice. Talk to your care team before you change anything about your insulin.