Hypoglycemia in non-diabetics

When not seeing patients, I spend my free time running ultramarathons of 50 miles or more. Last weekend, I experienced what I believe was a hypoglycemic event during a 100-mile race. Hypoglycemia as low as 30-50 mg/dL has been reported in endurance athletes. At mile 65, my legs became weak and wobbly. I assumed that it was due to fatigue from the almost 18 hours of running. However, suddenly I experienced severe disequilibrium. I was tremulous and unsteady. I had great difficulty finding my words.

Fortunately, I was running with a friend who immediately gave me some energy gel containing simple carbohydrate. I am not sure I could have opened the pack by myself. Symptoms disappeared within ten minutes. I have a new understanding of what my diabetic patients must experience.

We frequently see non-diabetic patients in consult for supposed “hypoglycemia.” Often this is an incidental finding on routine laboratory screening. Sometimes, there has never been formal confirmation of hypoglycemia; the diagnosis was made by their primary care physician based on symptoms alone. Some have been testing with their own or a family member’s glucometer. A few have had imaging studies looking for an insulinoma. Almost all have anxiety about their diagnosis. They have heard or read on the internet how dangerous hypoglycemia can be in people with diabetes.

True hypoglycemia is very rare in people who are not taking hypoglycemic agents. A slightly low fasting glucose is not abnormal; young healthy women may have fasting glucoses in the 50-60 mg/dL range. In addition, measurement by fingerstick glucometer is often unreliable, particularly at the lower and the higher ends of the range.

The most important aspect in diagnosing hypoglycemia is taking a thorough history. Is this fasting or postprandial? Have there been neuroglycopenic symptoms (mental status changes, dizziness, loss of consciousness, or seizure) or have the symptoms been only adrenergic (hunger, palpitations, anxiety, tremor, perspiration)? Are there any signs suggesting a more ominous process?

Whipple’s Triad must be met: confirm hypoglycemia by serum and not fingerstick glucose, observe neuroglycopenic and not only adrenergic symptoms, and finally, note resolution of symptoms after consuming carbohydrate. Most referrals do not meet these criteria and thus do not have hypoglycemia. I reassure these individuals that the incidental finding of a mildly low glucose is not of concern, even despite feelings of tremulousness and hunger.

I do not know with certainty that my experience was true hypoglycemia because I did not measure glucose at the time of the event. I am not a diabetic and do not carry a glucometer. In the future, I may wear a continuous glucose monitor for my own curiosity, realizing that continuous glucose monitors have issues with accuracy and that interstitial glucose does not always match plasma glucose.

A physician friend joked that if this happens again, I should write myself up as a case report. If I ever do, the readers of this blog will be the first to hear about it.