Marathon or 1/2 Marathon Experiences

As someone planning on running his first 1/2 marathon next spring (and maybe a full next summer), I’d love to hear about the experiences of others that have already done it. Details like: insulin adjustments, caloric intake, glucose monitoring, etc. would be great. I know that we each have to carefully figure out what works for us during our training, but some tips (do’s & don’ts) from people that have already been there would be great.

Hey Ken, I’m scheduled to run my first 1/2 on Nov 4th, so don’t have much experience to offer. Long run is only up to 8 miles. So far on the longer runs I’ve found it best to test early, after 2.5 or 3 miles to see how I’m trending and take in carbs accordingly. I cut my basal in 1/2 about an hour before I start the run, and only eat if I’m below about 160. Have found that “Sport Beans” (glorified overpriced jelly bellies) work as well as glucose tabs and go down better. Tried a Cliff Shot Block and it tasted nasty. Haven’t tried powerade or gatorade yet, but will before the 1/2. Good luck with your training. You’ve got plenty of time to figure things out.

I trained for and finished the L.A. in March, but I really was training in the blind. I ran with the Leukemia Foundation and my coach, as good as he was as a running coach, didn’t have much help to offer in terms of my diabetes except general things like ‘be careful’, ‘check your blood sugar’, and 'how ya feelin?"

What I did do was test every 30 minutes and make sure I had some carbs handy, either gels or glucose tabs. I also added Gatorade to my water bottle. I didn’t ‘carb load’ although I guess that’s possible, but I did always eat a good breakfast before my long runs and kept my bgs above 140 before a run began. Although I have a Dexcom CGM, I found it unreliable during strenuous activity.

I used to disconnect my pump when running, which was okay for a 30 minute run, but I found that on longer runs it led to ketoacidosis - burning, aching muscles, fatigue, nausea, thirst, fruity dry breath. Now I cut my basal in half during a +30 min run. I read of others who go on half basal for two hours before a run or race and back to normal for the race/run. It’s really a matter of trial and error.

You need to eat well after a long run, and include some carbs, but bolus for them. (I reduce my bolus by about 1/3 for the first few hours after a long run. Your mileage my vary.)

I bought a book entitled “The Diabetic Athlete” which is kind of technical but helpful. “Pumping Insulin” has a useful chapter on exercising and the pump and on using carbs (called Ex-carbs) to keep BG up during activities.

In any case, I ran the marathon and my BG went UP, probably because I didn’t carefully plan my regimen. I kept eating gels to keep my BG up on the assumption that it was lowering, even though testing indicated it was level.

Now I’m training for a 1/2 marathon in October and I’m paying closer attention. I still try to start with slightly elevated BGs. I carry my monitor with me along with some gels and tabs and the gatorade/water mix. I drink at regular intervals and test every 30 minutes. Afterwards I keep a close watch on my CGM and eat some carbs about an hour after exercising but reduce my bolus by about 1/3. I disconnect my pump if running under 30 minutes and go at half basal if longer. (I said that already, didn’t I?)


Do - keep your testing kit and fast acting carbs on runs of any distance. (If you don’t like carrying them, run loops and keep them in the car.

  • test every 30 minutes
  • keep hydrated
  • run with others - just in case (I break this one frequently)
  • pay close attention to BGs for couple of hours after run

Don’t - think you need to train that much differently than non-diabetic runners

  • use running alone to control your bg
  • Start running with a high bg - say over 270. This can be counterproductive. I don’t recall the mechanics of this, but it can lead to even higher bgs and ketoacidosis.

Do - run like a champion today.

Good luck with your training and the race!


P.S. there is a diabetic runners forum at the runner’s website That’s where I learned about


I recently ran a marathon, and found that a liter of Powerade / hr allowed me to run without a low for an extended period of time. I would go light on Lantus the day before, and make sure I was 100 - 150 before I began. On race day, I checked at the finish and was 107, after drinking a small cup of powerade almost every mile, which is commensurate with the liter / hr, I believe. I do not have a pump, so I cannot comment on my levels during the race. Above all, during training I strongly stress to run with others, a credit card and ID, or run around a track or small route where you can access to a phone, or help. My most scary moment came when I bonked and was far from home without an ID, money, or a phone with no way to get home but run. It was awful.


That’s good advice about the I.D. and credit card or cash. I prefer cash.
I also make sure that someone at home knows I’m going out and what route I’m taking.

I never go for a run without some I.D. because you never know when you’ll bonk.

Which I did on Saturday- half way into my five mile run. I walked back, though - no running. Good think I had some glucose tabs with me - I nearly decided to leave them behind.

I was not a runner and trained for 6 months to run my first 1/2 marathon 2 years ago. I use a pump and I was experiencing several lows for about the first 3 weeks of training. After about 3 weeks the lows during exercise stopped occuring. I would keep my pump on but turn my basal off about 1/2 hour before my run. If I was below about 120 I would have 15g of fruit carb and I never really fell low again the rest of my training. At the end of the race however my sugar was actually elevated (about 230) which I thing was from stress and adrenline. I would test my blood sugar about every 45 minutes when I trained but only once on race day. My other problem was the race was very early in the morning and I stayed at a hotel the night before, so my breakfast timing and type of food was a concern but it worked out.

Hi Ken!
I tested during training by running loops. Every 2 miles, I returned to my meter and every 4 or so I tested. I did the first half of my training without a pump (because I didn’t have one). After I got it, I adjusted my basal to 50% an hour or so before beginning and to 30% while running. I did not test during the race (I do not recommend this!). You should carry your meter and carbs WITH YOU, not with a friend. =o)

Good luck!