Rapid acting insulin taking twice as long to work as advertised

Hi folks, I’ve been a type 1 for a few years. As of late i’m becoming more aware of trends in my insulin’s action. I’ve been on Novorapid in vial form for most of my time.

The thing is that it takes quite a long time to kick in and effect my blood sugar levels. More frustrating still, it continues to drop my blood sugar up to six hours later, often abruptly at the end.

This combo means I suffer from long periods of high blood sugar and hours later a sudden low. I’m a bit tired of getting the worst of both worlds every meal/injection control-wise.

Has anyone experienced this? I am at a loss about what to do.

I’ve tried unsuccessfully to get answers from nurses and at endo clinics. I’ve tried Apidra in the hopes of it just being Novorapid specific or some sort of resistance built up to it.

If it is something like my body or specifically injection sites absorption being terrible what should my next step be?

Many thanks,

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This used to happen to me all the time but with Humalog. Have you tried pre-bolusing? It may resolve the issue of spiking right after a meal. Do you have a CGM? You might want to read Steven Ponders book Sugar Surfing? I haven’t read it but I’ve heard good things about it.

I wasn’t ever able to figure out the solution to my Humalog dilemma (I wasn’t on this forum at the time) so I ended up switching to Afrezza. There isn’t any long tail so no surprise lows hours later but because it is so short acting you would need to take multiple doses to control longer digesting foods. Also it peaks within minutes of inhaling so no need to wait to eat either.

I’ve looked into pre-bolusing which actually was what made me very aware of the insulin taking a long time to kick in. I’ve taken novorapid an hour before eating and seen very little movement which makes me feel like sometimes the carb spike is because the insulin is injected but not actually doing anything till a lot later. Maybe the long tail is the result of a delayed start… hmm.

I’ve got a libre when I can afford a sensor, I will definitely check out sugar surfing. I’ve been told about it before but I think I felt like I needed to have a more reliable insulin response first.

Sadly I don’t think Afrezza is available in New Zealand, but if it ever gets funded I will check it out.

Where do you inject? How many different locations? Is there any visible scar tissue? Even if there isn’t, you may still have scar tissue if you’re using the same spots repeatedly. Scar tissue can affect how well the insulin is absorbed/utilized.

What do you use for your basal insulin?

Do you exercise? It may be helpful to go for a short walk after prebolusing but before eating. Be careful that you have something on hand to treat lows though.

Exercise has a significant effect on how well and quickly the body uses fast-acting insulin.

A rigorous exercise routine can affect my insulin sensitivity for a couple of days after the workout.


Type one for thirty years, and I’m still trying to figure out this one myself. Admittedly, I’m only recently trying to be in much better control, instead of just riding the sugar coaster Things I’ve discovered thus far:

  1. When it comes to diabetes, bodies are STUPID, and usually do the opposite of what is needed. Such as craving carb when your BG is high, and not wanting to eat at all when it’s low.

  2. Similarly, when your BG is already high, you generally become more insulin resistant. Meaning, when you need it most, your insulin is going to take much longer to work. You will find your insulin needs and pre-bolus times vary considerably based on your current BG

  3. Insulin works fastest when injected into lean spots/muscle. I think most of us would rather do the less painful fatty areas, but just like fat in the food we eat slows carb absorption, fat in the injection site also slows insulin action.

  4. You may need to consider using longer needles. I’ve always been a little needle-phobic and was really excited when they started coming out with 4mm and 6mm syringe needles… But they slow my insulin WAYYYYY down.

  5. Inflammation = insulin resistance. This is i believe a massively unrecognized problem. Most people nowadays are suffering inflammation and not even knowing it because the aches and pains just become part of everyday life. Ask your doctor to run the “c-reactive protein” test for information. If it comes back positive, the first step will be to look for other auto-immune diseases diabetics are also likely candidates for. Then probably an elimination diet to look for food allergies. Environmental factors, like mycotoxins from mold, could also be at play.

  6. Exercise will speed up insulin absorption. Pre-bolus, then get your heart beating fast. It doesn’t necessarily have to be long or strenuous, you just need to get moving. Do jumping jacks in your kitchen while dinner is cooking. Jog in place. If you can escape, go for a pre-meal walk. Just be prepared for possible hypo. I was really shocked just how much faster my insulin works with just a little exercise.

  7. Similarly, hot baths/showers/sauna can speed insulin absorption. I find that pre-bolusing for breakfast before my morning shower helps even that sugar line out.

  8. If all else fails, slow your carb absorption with fats and protein to match your insulin activity. An apple by itself may be a recipe for DKA, but pairing it with peanut butter may just slow the carb spike to even your BG out to target range. Dare I even mention on a diabetic forum that if you want that waffle, it just may work out okay, so long as you add the bacon and egg on the side, too? :slight_smile:

Hope this helps!



Funny how the long-time D’s know this.

I started out with needles that were like harpoons in the 70’s. They were really much faster.

I tried some of the shorter needles when they came out, but I went back to longer needles. I use 8mm and sometimes 12mm needles and syringes, depending on how fast I need it. I don’t ever use 4mm or 6mm anymore.

Anyway, @Torh, everything Robyn said - 1 through 8 - was right. Try those things.

Declining renal function, which goes along with diabetes, can delay the body’s processing of insulin.

Like you my insulin peaks in working about 2 hours after I take it. It doesn’t mean it doesn’t start working within about 30 minutes, it just kicks in the most about 2-3 hours after the fact. And then it is still is working up to 6 hours later but in a much smaller effect.

So it gets a little tricky and I prefer prebolusing as much as possible. That keeps my sugars within the range of 100-170. I have a pump now and that way I can adjust all day as needed it’s easier and I don’t end up very often with those high numbers I used to get. It can still happen, but I usually just don’t go as high with the constant insulin from the pump.

Anyway a pump helped me in so many ways!!! But learning prebolusing was the first major help! I just have to prebolus about 20-30 minutes before I eat and it’s easier to not go high in the first place than waiting for it to come down after the fact.

Thank you so much for sharing all this wisdom!

@Robyn_H This has given me so much to think about.
I hadn’t considered environmental factors, my home has mold issues…
I’ll look into getting inflammation tested and renal function (thanks @Seydlitz!).

@katers87 I use my belly mostly, I try to move around it. I don’t have any visible scar tissue but there are definitely some harder patches. I wish I was on a smaller needle but i’m on an 8mm so can’t really go up in size like someone suggested. I don’t exercise very much at all but am at a good weight/bmi.

I use lantus for basal. I split my dose because I used to take it all before bed and found 4 or 5 hours later my blood sugar would dive a bit and cause a few lows overnight.

Try Apidra or Fiasp for your fast acting insulin.

Portion size matters, too. I find I have to eat small portions to avoid that high spike after meals. Of course, that means I eat several small meals rather than 3 big ones each day.

As people with diabetes, we have often heard about diabetes’ treatment characteristics that we somehow internalize as specific hard and fast rules. Our doctor’s, nurses, and CDEs also often believe these things.

We’re taught about insulin to carb ratios, basal rates, and insulin sensitivity factors. Seemingly implied in these exact formulas is all we need to do is discover what our personal formulas are and then we’ll be able to deliver the perfect insulin dose after we’ve carefully calculated the exact carbohydrate content. Unfortunately, diabetes does not work that way.

All these formulas, including insulin onset, peak, and duration are simply nominal numbers that will indeed vary from person to person and even in the same person from day to day and meal to meal. I like to think of these formulas simply as a way to get within the vicinity of my blood sugar targets and then use dynamic dosing techniques to home in on my target glucose level.

What are some of these dynamic techniques? If you have a pump, you could set a temporary zero basal rate if your blood sugar trend is moving downward toward your lower level. As a complement to that, you could inject 0.5 units of insulin to nudge a rising blood sugar back toward the center of your zone.

Strategically timed exercise, like a 20-30 minute walk immediately after eating if you’ve been fighting after meal highs is another way to nudge a wayward trend back toward the desired range.

I’ve discovered in recent years that while I am overall insulin sensitive (I take < 0.5 units of insulin per kilogram of body weight.), my relative insulin sensitivity is changing all the time. I am definitely more insulin resistant in the morning than I am in the late afternoon. Exercise and fasting both boost my insulin sensitivity while an over-generous meal and omitting exercise increases insulin resistance.

If I find my insulin resistance is becoming too much, I will often omit a meal and do a 16-24 hour fast. That will dependably turn insulin resistance toward insulin sensitivity. I find being aware of my relative insulin sensitivity helps me to take action to benefit my BG control.

You are right to be concerned about injection site absorption as that can definitely be a factor with long term diabetes. I had a two-day old perfectly absorbing insulin infusion site go bad last night as I went to sleep. My BG soared to over 300 mg/dL (16.7). What happened, I later found, is that blood fouled the site and essentially stopped or severely impaired insulin absorption.

I haven’t had a site go bad like that in months and months. I couldn’t have anticipated that circumstance and I just wrote it off due to the fact that I have diabetes. Sometimes diabetes wins, but certainly not as often as my will prevails.

Most of what I write about here will work best if the person uses a continuous glucose monitor. I think every person who lives with glucose metabolism disfunction will do better if they use a CGM. I know there are legitimate reasons people don’t use CGM but in general I think way more people could benefit from one. Deliberate navigation through blood glucose levels without using a CGM, to me, is like driving a car with a bag over your head!

You’ve received several good tips above. I hope your blood glucose situation improves for you.


I can’t thank you all enough for the responses. It’s refreshing to get so many different points of view on all this after so many frustrations dealing with single diabetes healthcare providers.

Hi Torth you have started a very interesting discussion. On insulin for 35 years I have seen written above things that I thought might be special only to me.

I note that you have a Libre Reader and of course with this you can see the graph of your BG which is so informative. You can also turn this into full CGM with the addition of a transmitter either the Blucon or the MiaoMiao. This enables you to set alarms on your phone (great at night) and see your BG unfolding every 5 minutes. If you do go for either of these then the app xdrip+ for android or Spike for IOS are generally reckoned to be the best.

If interested in this checkout my website bgonmywatch.com read the article “All about CGM”. Just bear in mind I am based in UK so some things such as price will be different.

I found the last step of getting it on my watch finally gave me the feeling of being in control (almost) of this infuriatingly unpredictable condition.

I have been on FIASP for eight months now. I was spooked a little at first thinking it would be dangerously fast from all the hype. I have not found that to be so. I really don’t see a lot of difference with Novolog. I will say this: FIASP does tend to have more bubbles which has caused some really bad highs for me like at night or when I can’t get home to change things out.

I have found Fiasp to be a fiasco, making little difference from older products. It is just a symptom of what the FDA noted in its ‘panic bulletin’ in 2008, which is that most drug development now represents just minor tinkering to avoid existing patents or to pose as incremental improvements sufficient to generate some profits. Medicine has entered a period of stagnation, beginning, according to a study by Gordon, in 1984, and while computers and space travel are advancing by leaps and bounds, medicine has to sit on its laurels of having overcome polio in 1954 as the last disease it has conquered.

This is smart. When I was using Lantus, I also split my dose to try to minimize the peaks and valleys. Lantus only lasted around 20 hours for me though, so there were still times when I had less basal insulin on board (1/2 daily dose). I use Tresiba now, and that has worked a lot better for me.

I’m also at a healthy bmi. I’ve read a decent amount of research that showed that exercising regularly can impact the development of cardiovascular complications. Exercise can help non-D people reduce their chances of cardiovascular problems, but it appears that it’s even more important for people with D. I’ve read that even a small amount of aerobic exercise weekly is better than none at all. I can post some studies if you’re interested.

If I spend a day very sedentary, then I’ll notice that my boluses just don’t work properly. However, if I get up and walk a few blocks to the store, the insulin kicks in. It’s amazed me how much a short walk can impact how well my body uses insulin after a period of time being sedentary.

Try it out sometime and see if it has a similar impact on you :slight_smile:

I’ve never heard of this test. Thanks for posting about it. I started googling to see if I could find more info, but then I realized that you may already have some great sites to reference. I figured I might was well ask! Is there a particular article or site that explains this test and the results of this test as it relates to diabetes?

I’m mostly wondering if there’s a chance that it might come back high simply because I already have an auto-immune disease (diabetes). Maybe my bg ran a little high one day so it might bump up the result of the CRP test.

If my bg is generally within a good, but not perfect, range, should the test come back “normal” as long as I don’t have any other conditions? At what level would you, personally, consider it an indicator of another condition?

Sorry for asking so many questions. I look forward to reading your response!

Here’s a good overview at the Mayo Clinic site of the c-reactive protein (CRP) test as well as the highly sensitive c-reactive protein blood test (hs-CRP). I’ve requested this test several times over the years. It’s a good marker for inflammation but not specific as to the source of that inflammation.

My view with respect to exercise is that unless I’m certain I’m going to live more than one additional hour for every hour I waste exercising, I’m not going to do it. We are homo sapiens, that is, creatures who are essentially thinkers, so why not leave the jumping to fleas and grasshoppers, the running to horses, and the log-lifting to beavers, since they are not only so much better at it, but they also have nothing else.