Post-Ultramarathon Recovery: Headaches, Fatigue & Potential Complications

Question
Dear Dr.Borucki,
 Hi,about three weeks ago my husband ran and finished a 100 trail race(in the time span of twenty three hours). Since the race, he wasn't bouncing back. Within this past week, he has been suffering from extreme headaches and fatigue. He also had a fever of 99 degrees to 100.7 degrees. He had seen his physician and was checked for Lyme disease and "Mono". Both came back negative. The physician say he has some type of virus. I am worried that he was dehydrated(he said that he was about 8-10 pounds lighter after the race). Could hyponatremia be causing these symptoms?? Do you think he needs an IV for rehydration?? How long should we wait until seeking further medical attention??  Thank-you for your help!!

Answer
I would have all those things checked... sodium, potassium, kidney function... the risk of extreme exercise and dehydration is muscle breakdown and that (CPK) can damage kidneys... I would have a CBC, BMP, CPK level checked and treated if indicated, otherwise, he may just need some time.... so the basic answer is get the above stuff checked now...