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Diabetes

2 hr glucose tolerance test long enough?

06/13/2008

Question:

Before starting Prednisone for Myasthenia Gravis, I was given a 2hr 75g glucose tolerance test. At the end of the test, I felt reasonably well, but was unable to eat a meal right away. At exactly the 3 1/2 hour time from consumption of the glucose, I started sweating profusely and feeling extremely weak, faint and sick. After consuming a large meal, I was okay. This, I realize is hypoglycemia. Does this mean that I am more likely to develop Diabetes with prednisone treatment? Should a 4 or 5 hr test have been done? Should I inform my doctor of this reaction or is this normal after the test?

Answer:

I am intrigued that your doctor was forward enough thinking to carry out the OGTT in that setting - it would affect my decision-making but it has never occurred to me to do that.

I would need to know more about you to interpret that test result for risk of diabetes but my gut feeling is that that it probably does not mean an increased risk for diabetes:  My experience is that low blood sugars do occur in that timing and I have seen them most often in young lean women, suggesting that the glucose load is stimulating a greater insulin response than is really needed for that calorie load and the people in whom this happens are very insulin responsive.  That would suggest a good backup capability for both making insulin and for responding insulin which will be a great help when the prednisone causes insulin resistance. 

I wish you good luck in facing your myasthenia and do hope you will write back at some time to let me know how you did with the prednisone.  You might want to print your question and my response out or cut and paste and send to your doctor.

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Response by:

Robert M Cohen, MD Robert M Cohen, MD
Professor of Clinical Medicine
College of Medicine
University of Cincinnati