Hi there! I have been type I for almost 19 years and have been active all of my life – used to be a dancer, have now switched to spinning, walking, running, elliptical, etc. In the last month, I have not been able to make it through an hour workout without going low, and it’s getting very frustrating! I turn my pump completely off and eat a large apple, a banana, and a yogurt cup about 45 minutes before my late afternoon workout, and wham! 1 hour of aerobic exercise, and I plummet instantly. I’m just wondering what other folks eat pre-workout. Maybe I need to add some protein to my snack? Thank you for your help!
Snacks help alot and I do recommend that. The snacks you are showing are exactly what I eat, although I add as much all natural pb as possible cause I love it so much. 
I find when I go low, it is because I have bolused too close to my exercise. My rule of thumb is that I wait for 2 hours to after I bolus for anything and then give 'er. Maybe you also want to carry dextabs or gel, or whatever form of instant sugar that can be quick and available during exercise. I tend to go low as well, so I check every 15 mins and if necessary pop back 3 glucose tabs. (maybe different to you and you may need more) Also, remember to have a snack with protein and carbohydrates after the workout such as meal replacement shake or, milk or whatever you enjoy. Goodluck.
You may want to consume some carbs during exercise. A sports drink might help, or some running gels or beans.
I doubt protein will keep up your BGs.
As Jeff says, avoid bolusing before exercise and test often.
Terry
Try a gel packet as you start exercising and maybee one half way thru.
I have been training for a half marathon and I’ve been eating a Luna protein bar before I run on Saturdays and find that 50-60 mins in I need to start eating a GU in order to keep my numbers up. As I was experimenting I found I needed something with protein to help me through the workout. Good Luck as you figure out what you need.
I agree with needing protein coupled with carbs. I eat an apple with peanut butter before working out. Also, make sure that you are accounting for your insulin acting time. Mine is about 1 hour to 1 1/2 hours, so I start my reduced temp basal generally around 3:30-3:45 pm for a 5pm workout, then cancel when I finish. About 45-60 minutes in on a long ride I’ll eat one of those cliffbar gel packs- they are gross but seem to work. It was also recommended to me to drink a glass of chocolate milk (I use almond milk) after working out to replace the glycogen stores in the muscles, depending on the workout I may need to bolus for this. This answer may have been overkill- there is nothing more annoying than getting low bloodsugar during a workout!
I typically have a package of peanut butter crackers (22gs) and lower my basal to 40 or 50% 2 hours before running. This works perfectly in the morning. In the afternoon following lunch I do the same thing, but also watch my IOB very closely… even then it’s kind of a crap shoot. 
Since you mentioned “late afternoon”, I’m guessing you have some insulin on board that is causing you to drop. I still have not perfected this, but I’m almost to the point where I will eat enough carbs to cover my IOB.
Check your insulin on board (IOB) next time and see if that isn’t the issue… and report back!
Thank you all for your hints and tricks! I know that insulin on board isn’t the problem - I usually haven’t bolused for about 5 hours prior to my workout. I think it must be a protein thing. I’m going to add Greek yogurt to my normal fruit snack tomorrow, and hopefully that will make the difference! Thanks!
I’m having trouble as well. I workout with a trainer for an hour around 5:30 and then do 1/2 hr of cardio. I’m trying not to use food much because I’m trying to get rid of some pesky pounds. I guess experimenting with the basal rate % and how far in advance to slow it down is the way to start to figure it out then.
My Dexcom has been wack lately and I’m sure I’m not the only one that HATES stopping in the middle of a workout to test!
4 oz of organic AJ with 1/2 portion of Whey protein 1/2 hour after has been working great to get me thru fixing dinner.
Thanks for the tips