Got questions about navigating life with diabetes? Ask D’Mine! Our weekly advice column, that is, hosted by veteran type 1 and diabetes author Wil Dubois. This week, we’re marking another time change as the clocks flash forward an hour on March 10. Wil has some specific diabetes-related thoughts on that, so read on…

{Got your own questions? Email us at}


Becky, type 1 from New Mexico, writes:  Blah. Time to change the clocks. Again. I hate the time change! It’s such a hassle. I have to reset the myriad clocks around my house, the appliances in my kitchen, my watches, and the clocks in both of my cars. So, really, does the time matter on my D-tech devices, or can I just leave them metaphorically flashing “12:00” like my grandmother’s VCR back in the day?

Wil@Ask D’Mine answers: Sorry, ya gotta update the D-devices. It matters. Trust me, it really matters. In fact, it matters waaaaaay more than you might think. 

Naturally, if you have a properly programed insulin pump, the value of having the time right should be obvious. But just in case it’s not obvious, let me tell you why it matters: Most pumps have at least four separate basal rates over each 24 hour period, and various insulin-to-carb (IC) ratios and correction factors (CF) for different times of the day. Would an hour’s error make a difference?

Damn straight.

Just for fun, let’s assume that your lunch IC ratio is on the aggressive side at 1:8, but that your dinner ratio is a more typical 1:15. The person who programmed your pump (most likely either an endo or a CDE) will have selected a single point in time to make the change between the two ratios, as no one has yet designed a pump with a smooth “curve” between settings. At one second the ratio is 1:8 and the next second it’s 1:15. From what I’ve seen, most pump trainers change settings right before the earliest time you typically eat a meal. That means if your pump is an hour off, it can easily be using the wrong math. In our example here, using the lunchtime ratio for dinner would result in nearly double the dose you need, putting you on the Express Train to Hypo City.

OK, so the IC ratio change outlined above might be an extreme example, but using it, it’s clear to see how even an hour’s error on an IC ratio can have a significant effect, and the same is true for the changes between CF’s. But surely, you say, what difference could and hour make on basal rates?

While it’s true that basal rates are more art than science, a one-hour shift in basal changes can mess with your blood sugar control more than you might suspect. That’s because, unlike basal shots (which come up below in our next reader question), it’s important to remember the short half-life of basal delivered from a pump. The current school of thought from most endos is that pumped insulin has an effective duration of action of three hours, so an hour’s error represents a full third of any active segment!

OK, so much for pumps. What about the humble blood glucose meter? Surely the meter’s clock doesn’t need to be reset, right?

Wrong! And there are at least two damn good reasons that your meter’s clock should reflect the reality of the surrounding world. The first reason deals with your doc. The second reason is yours and yours alone. 

OK, here we go: If your doc looks at your meter data, and he or she should, the time information is a critical component to making smart decisions about your treatment plan. Even being a short 60 minutes off can result in changes to your therapy that won’t be properly targeted. This also is true of CGMs, and there are times when your medical team will want to compare CGM and meter data, like when considering calibration times.

Now, for yourself, if you’re trying to post-game a blood sugar misadventure, you may find yourself scrolling back through the memory of the meter to try to piece together just what the eff’ happened to you. Slightly off topic, not too far off as you will soon see, my Fam and I recently got hooked on the Smithsonian Chanel’s Air Disasters and its sister program Disasters at Sea. Both programs, their titles notwithstanding, are actually thoughtful documentaries about after-the-smoke-clears investigations that set out to determine the causes of either (1) plane crashes, or (2) ship sinkings. And, as it turns out, the key to any successful investigation is good data from a variety of data recorders on the ill-fated planes and ships.

The same is true for you. It’ll be much easier to look back at your diabetes data recorders during a “crash” investigation, if all the information has the proper date stamps.

How good are PWDs about keeping up with time changes? Despite all the advantages, not too great. In my clinical days I found that a very large percentage of meters weren’t even set to the right year, much less the proper month, day, and time! Why? I suspect it’s because most diabetes devices, and especially meters, have poorly designed user interfaces. Or put another way: It’s just damned difficult to figure out how the heck to change the time on them.

My advice? Keep the quick-start instructions for your D-tech devices in your battery drawer so you can find them when you change your smoke detector batteries at the time change. Uh… you do change your smoke decor batteries when we spring forward and fall back, don’t you? 

So update your D-tech devices. All of them. Tonight. But that said, I’m with you on the “blah” factor when it comes to time changes. I say come this autumn, let’s all fall back a half an hour and leave it at that!


Victor, type 2 from Colorado, writes: Back to Daylight Savings Time! Any tips on how I should deal with my basal insulin? Should I try to ease into the change, or is one hour not really going to matter? 

Wil@Ask D’Mine answers: In a perfect world, you’d want to make the change over a four-day period, adjusting your basal shot time by 15 minutes per day to avoid either overlaps or gaps in the coverage of the insulin.

But in case you didn’t notice, our world is far from perfect. 

Most PWDs take basal either at bedtime or when they get up or — like me — at both times. Now, I can’t speak for anyone else, but my life is chaotic enough that I don’t have either a set bedtime or a set time to get up every day of the week, and I suspect I’m not the only one. This means that there’s already significant variation in my dosing times. Doesn’t that set me up for gaps and over-laps? Yes, but they’reoverwhelmed by the chaos of my life. Variable stressors. Carb-counting faux pas. Missed shots. Plugged pen needles. What’s that? We’re supposed to change them each time? Really? Plus hidden carbs, sleep disturbances, weather…

There’s so much other crap going on, I don’t notice the difference. How much crap? Our buddy Adam Brown at diaTribe has counted 42 separate factors that can affect blood glucose, and I’ll bet that, despite his brilliance, he’s missed a few.

So for most of us, given the chaos we live in, combined with the 18-26 hour duration of basal insulins, it’s unlikely that an hour’s difference in injection time will cause a difference that is noticeable.

Now, this is different from the advice I gave pumpers above, and there are two elements a play here. The first is that the duration of action of injected basal is up to eight times longer than fast-acting insulin pumped for basal coverage, making the impact of an hour less in the overall scheme of things; and the second is the frequency. If your pump clock is off, you’re effectively taking your basal at the wrong time, several times a day, every day. That will mess up your therapy. But the shift of a basal shot, by one hour, twice per year, is going to disappear into the background static of life.

So I’d just spring forward and take your shot at the “new” time. Right after you change your smoke detector batteries, that is.


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. Bottom Line: You still need the guidance and care of a licensed medical professional.