Wil Dubois

Need help navigating life with diabetes? Ask D'Mine! That would be our weekly advice column, hosted by veteran type 1, diabetes author and clinical diabetes educator Wil Dubois

This week, Wil takes another look at a common question often posed by those of us in the Diabetes Community: What do I do if I miss an insulin dose? Happens to us all, at times, and it's always good to refresh our knowledge.

{Got your own questions? Email us at AskDMine@diabetesmine.com} 

Pete, type 2 from Florida, writes:I have been struggling with diabetes for 5 years. I will sometimes fail to do my shot before dinner and wonder if I should take the 40 units when I remember? Or wait and take it before bedtime? I am looking for guidance. I am tying to find a path that works.

Wil@Ask D’Mine answers: One of the universal things we insulin users suffer from — no matter what type of diabetes we have or what type of insulin we take — is the missed shot. Yep, when it comes to life on insulin, the old rodeo adage of it’s not a matter of if you get hurt; it’s only a matter of when you’ll get hurt can be translated directly into diabetes: It’s not a matter of if you will miss a shot; it’s only a matter of when you will miss a shot.

We talked about this briefly a while back, but it’s such a universal problem that’s so much more complicated than it looks on the surface, that I think it’s worth revisiting today. So here’s Professor Wil’s quick course on the inevitable missed shot dilemma:

Types of Insulin

There are two main kinds of insulin: The fast ones and the slow ones. We’ll start slow. Actually, no. I changed my mind. We’ll start fast, because the answer for a missed fast-acting insulin shot is, well, faster.

The fast insulins are Apidra, Humalog, and Novolog. One member of this unholy trio is used by all type 1s, and some type 2s, to “cover” meals and to correct high blood sugars. As such, a missed shot usually happens around meal times, and as anyone who needs one of these insulins that eats three meals a day takes 1,095 injections a year for meals alone, it’s gonna happen.

Did I Miss an Insulin Dose?

Once the inevitable happens, first and foremost, you need to be really, really, really sure you missed the shot. Really sure. It sounds crazy, but when you are halfway through the linguini, it’s sometimes impossible to know if you actually took your shot or not. When in doubt, in any doubt at all, skip the shot, because the worst thing you can do is overdose on fast insulin by taking twice as much as you need.

But if you are 100% sure that you forgot, and you are within 30 minutes of the meal, you should take it at once. If it’s been more than a half an hour, you are probably better off using your correction factors instead to fix the high you just gave yourself. Because at this point the sugar is ahead of the insulin, and a meal shot that late out of the chute will never catch the bull. Modern fast insulins generally take 20 minutes to start working and won’t peak for two hours. If you miss the boat by more than a half an hour, jumping off the pier after it will only result in taking a bath.

In a tweet:

"30 minutes or less, shoot the meal. 30 minutes or more, correct the sugar."

How Fast Does Insulin Work? And Afrezza Inhaled Insulin?

Oh, damn, I guess I need to include that new Afrezza in the fast crowd, too, don’t I? What to do about a missed huff? Well, hell, I don’t know. We’re all still learning how this stuff works and how it is best applied, aren’t we? That said, I suspect you might actually be better off with a late huff than a late shot, because the powered insulin has such a faster onset and a shorter run. In fact, I wouldn’t be surprised if this stuff becomes the go-to backup med in the future for liquid insulin users. The prescription label will read: Take one huff for missed fast-acting insulin shots.

Now let’s slow it down. Here in the states, the slow insulins are Lantus, Levemir, NPH, and U-500. Did I leave anyone out? Oh, yes, I see you waving your pen back there in the last row of the basal hall. Slow insulin now includes the new Toujeo. And overseas there are some others, and at least one of these may be coming to a neighborhood pharmacy near you soon. I can give you some blanket advice for the old guard, but it probably won’t apply to the new kids, as the next generation of slow insulin is a whole ’nother kettle of fish. They seem to be largely immune to injection timing thanks to a newfangled black magic I have yet to get my head around.

Lantus and Levemir are basal insulins that last more-or-less 24 hours. That means the shot doesn’t impact just the here and now; it has effects that reach far over the horizon into the next day. If you take a shot late one day and take it on time the next day, the action of the two shots overlap. This is called stacking. It can, for a time, create a double-dose of insulin in your blood.

Missed Insulin Injection

Of course, ask your doctor, blah, blah, yadda, yadda, but in general, the standard rule of thumb is that if you missed the basal boat by more than two hours, you should catch the next train instead. Oh, wait. I think I changed hats in the middle of the stream again and mixed my metaphors.

Anyway, the thought behind this is that the tail of extended insulin is weaker than the main run, and the onset of the next shot is not instantaneous; therefore some overlap is acceptable. And the same thinking goes, that the longer the overlap is, the higher the risk of a low is, and that because one high day is less of a health hazard than one bad hypo, the lesser of evils is to skip any shot that has been missed by more than two hours.

This works great in PowerPoint slides, but in the real world it doesn’t always work out so well as basal insulin actions times actually vary with the size of the dose, the brand, and the biology of the individual user. Still I think you are “safe” taking a shot 2-3 hours late if you take one shot a day. Just be aware that you are at increased risk for a hypo following the next shot, and stay alert to your blood sugars during that time.

Of course a great many people using basal insulin take two daily shots, often of different doses, to deliver a higher level of basal during some parts of the day, so this complicates the matter a great deal both because the overlap period of a late shot is much longer, so you have to ride out a longer stacking period, and because you’ve changed the shape of the action curves between the pair of normally synchronized shots.

What To Do?

In this scenario, I think you should shorten your late-shot window by half. You are safe 1-to-1 ½ hours late, but beyond that it gets risky.

An alternate game plan that some D-folks use is to take 50% of a missed shot, on the theory that it will take the edge off the high that a period of no basal would cause, while reducing the height of the stack.

Briefly, the NPH and U-500 products have pronounced humps, like camel’s backs, in the shape of their action curves, being most powerful at the midpoints of their duration of action. Shifting shot times is doubly dangerous as this can place these areas of increased potency at times where you do not need them. In my book, a missed NPH or U-500 shot needs to stay missed. Screwing with the timing is dangerous.

In a tweet:

"If you are too late to the party, you’ll be early to the low."

What do I personally do? Well, hell. When I forget a shot, I’m not likely to remember that I forgot it at all, and I spend the next 24 hours wondering what the #@$!%&# is wrong with my damn diabetes this time!

One last word. You said that you struggle with your diabetes and that you are seeking a path that works.

That’s a column in itself. So that’s exactly what we’ll talk about next week.


This is not a medical advice column. We are PWDs freely and openly sharing the wisdom of our collected experiences — our been-there-done-that knowledge from the trenches. But we are not MDs, RNs, NPs, PAs, CDEs, or partridges in pear trees. Bottom line: we are only a small part of your total prescription. You still need the professional advice, treatment, and care of a licensed medical professional.