Duration of Humalog vs Novolog in cartridges

I remember reading the following before I attended Tandem training;
Replace the cartridge every 48 hours if using Humalog; every 72 hours if using NovoLog.
At the time I was using Humalog for MDI as my insurance would not approve NovoLog😬.

I was instructed to change the cartridge out every 3 days, even with Humalog, and my supplies are consistent with every 3 days.

I have noticed that day 3 requires larger corrections and override boluses than days 1 and 2.

Does anyone know why Tandem recommends 2 day changes with Humalog and 3 day with NovoLog?

My next delivery of insulin is going to be NovoLog, so I will see how that works for me.


This is so very interesting. I am on humalog and remember asking in 2021 when I was on t-slim for a hard month about changing insulin and my NP said we could. I quit before trying it and wonder if besides the tunneling issues, this is an issue for me. Sometimes after tons of corrections past 2 day mark, I will change it without seeing bleeding or having insulin smell and the pod looks normal upon removal. I hope people will chime in if they started humalog and moved to novolog. Thanks for bringing it up.


My 2 c:

I started on Novolog and switched to Humalog thanks to my insurance changing its formulary.

I asked my endo if there was any difference and he said they were the same.

I’m not very precise in my tracking of stuff - and leave it up to Control-IQ. That said, I haven’t detected any difference between the two.

And I have a confession: I change out the tandem cartridge every 4 or 5 days. I fill it up to 300 ml and change it when it runs out. So I try to get the most life out of my set.

My only issue with keeping the cartridge this long is that occasionally I will get “occlusion alarms” towards the end of the session (day 4 or 5). This might be due to issues at the site, but it could also be a number of other things; idk.


A blast from the past by @Eric with several studies that conclude that NovoLog (Aspart) is more effective in continuous infusion (pumps) than Humalog (Lispro). Sometimes GOOGLE is your friend.


Like bostrav59, I use Humalog for 5 or 6 days in the cartridge (but change the infusion set every 3 days to reduce the possibility of scarring.) I haven’t experienced any problems with this. And the FDA has approved both Humalog and Novolog in pump cartridges for several days (I always have to look it up, but it’s something like 6 days for Humalog and 5 days for Novolog, or maybe it was 7 days and 6 days respectively or something. It’s in the fine print on the huge paper instructions that come with each vial of insulin.)


I am always super happy when Google turns up stuff we have here on FUD!

Go to Google and type “car baked insulin”. First link, baby! :grinning:


Yeah, baby! :drum:


We are also first link with the search term, “freezing humalog”

We are making a difference. Probably should repost that one with insulin which is a more generic search term.


@CarlosLuis My old Endo considered switching me to Humalog from Novolog to allow MDI 1/2 unit dosing (she couldn’t find a 1/2 unit Novolog pen). She said their were very few differences and none should apply. I wasn’t on a pump at the time, so will be interested in responses you get on this for possible future use…


I know you are on a pump now, but for anyone else who is having difficulty getting switched over to a certain type of pen for the purposes of getting 1/2 unit dosing, there is actually a poor-man’s answer!

You can buy sterile vials on Amazon for very cheap. You can also buy BD syringes that have 1/2 unit markings on them. (Almost all states allow the purchase of syringes without a prescription!) You can get them from the diabetes supply websites, like https://www.adwdiabetes.com, or a million others.

So you take your full unit pen and inject the whole thing into your newly acquired vial. And then you use the 1/2 unit syringe to be able to do 1/2 unit dosing.

Simple, right? :man_shrugging:

The only trick is that when you inject the insulin from your pen into the vial, you gotta remember to remove the same amount of air to relieve the pressure in the vial.


I received my shipment of NovaLog yesterday and will be changing site and cartridge later today. I am a reader of all sorts of stuff including instructions and medication insert sheets. I was surprised by this bullet point on After vials have been opened - There is the usual room temperature or can be refrigerated after opening and to discard any left after 28 days. Here’s the surprise - “If using NovaLog in a pump, throw away all opened NovaLog vials after 19 days.”

I took a look at a Humalog sheet. There is nothing like that - just discard after 28 days.

This enquiring mind wants to know why? Is there a degradation of NovaLog that makes it less potent after 19 days. It’s not a big thing for me. I tend to use a vial in 20-22 days. I just don’t like not having an explanation.

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Because the vial will KNOW and will STOP WORKING. That’s a ridiculous bullet point statement and I never throw away insulin, ever. There is NO expiration, regardless of what any bullet states. It’s too expensive to throw away and extensive testing by myself and others on this site has born that out. There is no degredation that I have seen (except on 1 occasion which I made a post about). I use 1 - 3 year old expired insulin in our son all the time and it works just fine. When I open it, I use it until it’s gone…if that’s a day or 3 months, I use use it all.

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“If you use the Novolog insulin from your VIAL in a PUMP, your insulin will stop working after 19 days…you MUST throw it away!”…

wizard of oz GIF
(pay no atention to the man behind the curtain)

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@CarlosLuis That’s just plain odd! I’ve never heard (haven’t read an insert, I use pens and one of those lasts at most 9 days), but have always understood the 28-day dispose rule. Perhaps they meant don’t use it to fill a pump cartridge past day 19 thinking it might last in the cartridge 9 days? Can’t figure how insulin in a vial would “know it was going to be used in a pump!” Obviously written by some one that knew what they meant, but didn’t communicate it very well! @ClaudnDaye has it!

I got off the phone with a very good person at Novo Nordisk. She found it on the insert, but was unable to answer why. She said she is going to find the answer.

I read NovoLog directions online, pretty much the same as the insert minus the 19 day thing. I joked with her that I may be the only person ever to read that insert.


This is being misread, “* For insulin pump use, the total in-use time is 19 days, including 7 days pump in-use time.” It does bot refer to a vila, but only to in pump use as in the chart.

It is stating that the insulin in use in a pump container is limited to 19 days, 7 actually in the pump hardware.


Interesting but what I typed in is exactly what was printed on the insert.
“If using NovaLog in a pump , throw away all opened NovaLog vials after 19 days .”

“Throw away all opened NovaLog vials after 19 days.” This is an exact quote.

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I fill my Tandem reservoir to 300 ml and use about 30 per day, so it lasts me for ten days. I change the infusion set every two days, but use the whole cartridge. Have to fight the Solara/PumpsIt people to keep them from sending me a new reservoir with every infusion set. If there has ever been degradation I have not been aware of it. Carry my pump on my belt rather than in my pocket, so it’s a little cooler that way. NovoNordisk must have some good reason for the advice they put in the insert, but I don’t know what it is.



I’m not sure about the rest of you, but I smell a lawyer and executive combo intent on maximizing profit based on how the stuff was tested for the FDA…not that the FDA had anything to do with it other than approving the label…ok, the FDA is complicit with the blood-sucking corporate lawyer and executive that developed the wording…

So, a magical potion that has a 28-day usable lifetime in a sterile container (pen, vial) gets cut down to a 19-day usable lifetime because its transferred from one sterile container via a sterile syringe into another sterile container (pump) and the only other change is potentially a rise in temperature above 86 degrees, depending on the weather and working conditions of the person carrying the last sterile container… I don’t see what’s so hard to understand…makes perfect sense! :innocent: :zipper_mouth_face:

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The statement in the insert plainly states to discard any the vial. It does not refer to insulin in a cartridge. I think elsewhere the limit in the cartridge is 7 days.