Proven formula - rough draft

This formula will allow for management of insulin levels and carb intake for endurance cycling. All credit goes to Marcey Robinson, MS, RD, CDE, BC-ADM. Please use this at your own risk. This information is my strict adaptation of her practices. Google her to appreciate her knowledge of diabetes and sports!

Proven Method for rides over 90 minutes in length. Based on 150 lb athlete.:
  1. Eat 50 grams carb breakfast 3 hours before ride.
    1. Dose at 1/2 to 2/3 reg. bolus.
    2. Replenish glycogen stores in muscles lost overnight
    3. Allow 3 hours for insulin to clear system
    4. Get up early to eat and return to sleep if possible
  2. Target BG levels of 130 to 160 at ride start.
  3. Reduce basal 20% at start of ride. If you are dropping 30-60 points per hour, your basal rate is too high. Do not stop your basal.
  4. In first 45 min- drink 20 oz sports drink with electrolytes, maltodextrin (complex carb) at 35 grams carb. Do not bolus.
  5. For each consecutive 45 min- eat 35 gram gel with Maltodextrin or drink sprt drink detailed in step 4. Do not bolus.
  6. Reduce basal up to 50% at hour 2-3. If you are dropping 30-60 points per hour, your basal rate is too high. For extreme endurance events, basal can remain at norm or even a little higher.
  7. For each consecutive hour where sport drink was not consumed, drink 20 OZ water.
  8. Carry simple carb gels for treating lows. 35 gram Honey Stingers.
  9. Eat 45 grams carbs and 45 grams protein post ride. Bolus at 50% to 65%.
  10. Keep basal lower for up around 24-36 hours post ride.
  11. Numbers vary up to 20% by individual.

Are there any guidelines for Type 2s not on insulin, and/or PWD who keep tighter control? (I try to stay between 90 and 120 at all times, and unless I’m bingeing on carbs big-time, I’m reasonably successful at it EXCEPT when I’m cycling.)

If I’m on a long ride where I have a planned break (riding to/from a planned destination or running errands), if I’m below 110 I can deal with something like a Larabar (190 cal, 12 g carb, 4 g protein) at the one-hour point and be OK at the end, but I’m still at sea where it comes to rides without naturally-occurring breaks or where my blood glucose level is over 120. (I’m finding some of my 2±hr training rides I’m ending in the 140’s, which is a lot higher than I’m comfortable with, and that’s without consuming more than 100-200 calories over the length of the ride.)

My hydration is weather-dependent: on a hot, humid summer day I need to do 2-3 sports bottles per hour, one straight water and the other low/no-carb electrolyte fluid (e.g. Propel, Ultima Replenisher, etc.); the electrolyte fluid will serve to keep my blood glucose over 100 and my blood pressure in an acceptable range. On a cool day, my fluid needs are about half that.

Sorry tmana - I don’t know of any right off. I’m sure there is good stuff out there. Start with the book “The diabetic Athlete’s Handbook” by Sheri Colberg.

I would offer the following: Tight control isn’t everything. If you don’t exercise your heart, lungs, etc., and stay strong and flexible, what’s the point in very tight control? In terms of potential complications, the difference between an A1c of 6.0 and 6.3 is not huge. And if it takes some swings to 140, so what? If you got your heart rate to 150 for an hour, you did more good in the long run.

You may be drinking too much water. If you drink too much, your body can’t absorb the carbs you need as well. See a really good discourse at Hammer Nutrition’s website.

The formula I follow is intended for rides over 90 minutes in length, with physical output pretty high.

Keep riding and have fun!

If anything, I may not be drinking enough fluids (particularly electrolyte-replacement fluids) on long rides in hot, humid weather: I’ll return home a bit dizzy, with my blood pressure low enough for the next half-hour that I’m on the verge of passing out (I’m under doctor’s supervision for HIGH blood pressure); trial and error proved electrolytes to be the key factor in those conditions.

The general point for me is to exercise AND remain in tight control at the same time. Until about May or June, I had no trouble maintaining tight control on rides of 20-30 miles (1.5-2 hrs at an average of about 12-13mph, which is about as fast as I can go on anything not a downhill, for any distance longer than a sprint). It’s a new development that I’m trying to figure out how to deal with.

I guess when you’re a Type 1 like me ya just gotta forget about the idea of remaining under 140. At least if you have to eat lots of carbs to ride. I guess I’ll live with an A1c in the low 6’s and riding thousands and thousands of miles a year.

If you have to pee when you ride you’re drinking too much. You might use that as a measure.

Umm… Rule of thumb I was taught re: renfaires (when we’re strolling around hot and humid environments wearing 15 lbs of steel and brocade): if you don’t feel the urge at least once an hour, you may be dehydrated. Sadly, there are days on whch I can consume a couple gallons of water at faire and retain the lion’s share of it until some time around midnight…

FWIW, I spent most of the Tour de Cure somewhere in the 130’s – possibly because I kept downing those contain-no-real-ingredients Tour-provided PBJs and refilling my electrolyte bidon from the Gatorade provided instead of doing something more reasonable like eating my own protein bars and using cold water to mix my own electrolyte fluid.

No offense, but your rule of thumb about hydration is outdated and wrong. Read the research at And/or check with an expert - that’s what I did. She trains diabetic triathletes. There is modern science behind the “formula” I posted. It is aimed at Type 1’s, with lots of applicability for Type 2’s. Obviously everyone is welcome to use whatever method they prefer. I posted this at another member’s request, and I encourage those engaged in endurance cycling to try it.

Best of luck to all!

Interesting that someone could put figures to this. I see diabetes management as a day-by-day game that really follows few rules. I also have a hard time sticking to a routine, so I try to find what works in various amounts. I generally don't ride 90 minutes either - usually more like 20-25 for the commute, 2 hours for the evening races at a high effort, or 5-12 hours on a long weekend rides.

I aim to start around 150-180, expecting that I didn't adjust basals until shortly before leaving, so I'll probably drop another 30-50 when I get moving. I'll turn basals down to -80%. Watching my Dexcom, or if I don't have that than I check my bgs when I can (usually about 2 hours). If it's heading down, than I'll eat some dense carbs such as clif bars, sesame sticks, or granola. I sip G2 gatorade throughout the day, usually 1 or 2 bottles but depends a lot on how hot it is out. I try not to ride when it's sustained over 90F during the day, or at least take a long lunch stop on those days to cool down and really rehydrate. I often carry a third bottle, which is a collapsible Platypus container that I'll just drink from at a water stop and maybe leave half full if I don't know the next stop. Lunch varies depending on who I'm with and where I've biked to, but I usually just continue to eat my snacks and maybe buy something that's higher in fat and protein instead of carbs, but still not taking in large amounts at a time. For quick fixes, I have a waterbottle with flattened soda (or sometimes juice when it's colder out). More dex tabs in the bag if I want sugar without the liquid.

Usually there's some fruits in there as well. I'll bring along an a few apples, pears or bananas. Sometimes a few celery stalks. Usually something has a dried fruit in it, otherwise I'll add more raisins or dried apples or bananas. I'm a big fan of "real food" during activities. Most others seem to use maltodextrin and expensive substitute foods like Gu or Hammer products, but I can't stand protein drinks or other faux-foods. I'd say a real food diet while exercising is just as good (if not better) because I've done 15 rides over 100 miles in the past two years (some up to 150 miles) without cramping up or feeling like I wasn't eating right. Usually after a ride I eat a bunch of protein, usually good cheddar cheese.

I know you posted this almost a year ago, but I wanted to say thank you. This has really helped me adjust my endurance ride nutrition. Especially the pre-start regimen. Just wanted to share!

MegaJ - very cool. glad it helped. Science works when you listen.