I am a 47 year old male who has had diabetes for 16 years. I exercise often and am currently training for an ultramarathon, a 50 mile trail run. I have run four marathons in the past, however, at the end of three of these marathons, I have experienced low blood sugar and nausea. My best run was in 1999 when I took my glucometer with me and checked about every hour, I finished at about 140 mg/dl [7.8 mmol/L], but was very nauseated.

Currently, I am currently using 15 units of Lantus in the morning and between 20 and 30 units of Humalog depending on my activity level. For longer training runs, those 15 to 25 miles, I take less Lantus and almost no Humalog. The big problem I am having now appears to be dehydration and nausea.

A couple of weeks ago I set out to run 30 miles and was only able to make it 16 miles before I had to stop. It’s like I’m dehydrating while I’m drinking water. I lost almost a full stomach of water, but I still lost 12 pounds that day. I’m fairly stocky. I lift weights, am 5 feet, 10 inches tall and weigh about 225 pounds.

I feel like I could go the full 50 except for the dehydration and nausea. After my run a couple of weeks ago, I went to the doctor’s office to get an I.V. so I could get back some of the fluid I lost. One of the doctors said that diabetics can’t stay ahead of the dehydration that comes with ultra-running. Is there a reason this happens? What can I do about it?

A marathon is huge endeavor for people with diabetes not to mention an ultramarathon. Endurance athletes can become dehydrated, especially in hot, humid weather or even more so at high altitudes. Running in high altitudes, the body tries to adjust to higher elevations by more rapid breathing and increased urination. The faster you breathe the more water vapor you exhale causing dehydration. The longer one exercises, the more difficult it is to stay hydrated. Dehydration can also be cumulative over a period of days. For this reason, it is important to keep hydrated on the days leading up to the ultramarathon.

How do you know you are dehydrated? A guide is to monitor your urine. You should drink enough fluids so that you are urinating frequently. If your urine is dark and has a bad odor, there is a good chance you are dehydrated. During race times it is probably a good idea to drink at every water stop. For activity under one hour, water is sufficient, but anything over that (i.e., ultramarathon) Gatorade or PowerAde (any fluid that has a combination of carbohydrates and electrolytes) is recommended. It is important to replace sodium to prevent the risk of hyponatremia (low sodium) which can lead to poor performance.

Prior to a race, a good guideline is to drink 16 ounces of water an hour prior, eight ounces 15 to 30 minutes prior, and four to six ounces of fluids containing carbohydrates and electrolytes, every 20 minutes, over 60 to 90 minutes during the race.

The take home message is to have a plan to keep hydrated in the days leading up to the race, the time just prior, during and after the race.

RP