What Causes Tiredness, Dizziness And Disorientation?

My husband is 40 years old all day today he had been feeling tired and disoriented late in the evening i found him on the floor, but he does not remember how he got there. He did say he had a couple of dizzy spells during the day, he is not a big eater. And he stresses himself out more than normal with work and side jobs he has going on.