First Duathlon...suggestions for training and when to check BG


I am doing my first Duathlon (2mi run, 20 mi bike, 2 mi run) in a few weeks and I am a little nervous about what my BG will do. I have only been T1 for 7 months and I am still not fully dialed in as I think my honeymoon is coming to an end(of course at the same time as the race!). So, everything is changing and I am worried what will happen during the race. I do have the Dexcom, so that will help, but it is usually behind about 15 minutes when I cycle. Should I actually stop and test mid cycle or just go by dex and hope for the best and test at transition? Any suggestions about what to do and how to train would be great!!

Hard to say with the changes the end of your h'moon may bring... but...

I just listen for the telltale zzzz.... zzzz... zzzzz... of the Dex and know I gotta take something in right there and then -- actual number doesn't even really matter to me all that much, so I don't stop to test to get it exact. I don't even take it out of my pocket as I know what the warning is all about: No doubt there will be arrows pointing straight down because of my high output! So even if I am at, say, 157, if there are two arrows pointing down, I will right then take in some carbs to hopefully head off the bonk. It really is what the Dex excels at (for me).

Good luck!


Go by Dex, test at transition.....also do a test/mini Duathlon to see what numbers you get and test to see how close they are. I use my Dex with riding daily and its pretty accurate and watch for the arrows and react to that. My best advice would be just to test it out with training at or near your Duathlon level prior to the event. Good luck. Have fun.

What is a good pre-meal before a duathlon? It starts early (7:30am), so I am wondering how much before I should temp basal? Should I reduce my bolus, too?

I would use the Dex during the stages and test at transition. Consider that increased adrenaline causes sugar spikes in a lot of people before races or events as well.

I'd also work on training for nutrition just as much as training for the event. I would recommend not planning a meal that you haven't tried several times prior to a training ride/run before, last thing you want is to overeat or eat something that causes you to feel less than optimal during a race. So far I've been doing full boluses on meals preceding a ride, I don't like the way my body responds to elevated sugars during exercise and fear reduced boluses would cause this to happen.

I personally set my temp basal when I pull into the trailhead parking lot when going out for riding. Still working on the ratio of carbs to exercise duration.

My suggestions are...

  • Nerves will raise your sugar.
  • Dehydration will reduce the accuracy of the Dexcom.
  • Test at transitions.
  • Rely on the dex.
  • Pick a target BS to start with. I like 150mg/dl.
  • If you have a high HR (over 170 for me), or your body isn't used to that kind of effort, your BS may climb.
  • If you maintain a mid-range HR (120-170 for me) and your muscles are fully trained, your BS may drop.
  • Keep some sugar tabs in your bike bag.

Focus on the event though, and have fun. If I could have someone else monitoring my sugar during an event, and stop worrying about it myself, then my sugars could be so much better, and I could enjoy the tri/run/bike/whatever.

Hi MeganB! Congrats on training for your first duathlon as a type 1! (I did my first tri 3 months after my diagnosis).

This is my experience: I've learned to wake up about 4 hours before my event. Eat a good breakfast (like oatmeal with fruit) and bolus the normal amount. Then I go back to sleep if I don't have a commute to the event. I will check my BG 30 min before the event, and if it's lower than I'd like, I'll eat a snack _without_ bolusing. I set my basal to 4-exercise (animas pump), which is programed to go to -50% 1 hr before the start of the race. If it's a long event the basal rate will increase to -40, -20% successively to account for the carbs I'm taking in.

As far as dexcom and testing goes, I would definitely test at T1 and compare to your dexcom reading. If the arrow is flat and the numbers are relatively close I will rely solely on my dex, if the arrow is going down and there's a discrepancy b/w dex and the meter, I'll eat than probably stop to check halfway through the bike, just to make sure my BG is at where I really think it's at. And of course test again at T2. Also prior to the event during training, test, test, test. If you stop during training and learn how you respond to various exercise intensities, you'll have a better inkling race day. (Not to say that diabetes doesn't sometimes throw all the rules out the window).

A great resource to look into is TeamWILD. I have an olympic triathlon in 2 weeks and have been training with them. They're amazing and wonderful and know their diabetes training! Working with them has taken most of the guess work out of endurance sport and diabetes for me. The more I know and prepare, the less anxiety I have about BGs. Another group of active diabetics can be found at

Good luck on your Duathlon, and let us know how it goes!

Thanks for the great info! I had looked at TeamWILD's website, but haven't pulled the trigger yet because of the price. I may work with them in the future.

I wonder if I get up at 4am to eat if I could fall back asleep. I don't want to be tired for the race..hmm.

I am off to train ;) I sometimes decide to exercise at the last minute which will be just 2 hours after bolus...should I eat more or temp basal more? I usually need 3 hours to get bolus out of my system as well..

Please write us a race report after the event! I always enjoy reading how others make it through!

I hate that dilemma of wanting to exercise after a meal. I miss that flexibility I use to have before diagnosis. I personally have to think about how large the bolus was. If I took a lot of insulin, I absolutely cannot workout within 3 hrs of that meal and have horrid lows if I do. I think you just have to figure out your personal tolerance for it.

Also, don't try the 4am wake up for the first time on race day!!! Never do anything new the day of the race!