How much hair can I expect to lose from telogen effluvium?

There is no quantifiable number to say how much hair you may lose from telogen effluvium because everybody is different.

No, there are no definite statistics.But individuals with telogen effluvium from fever can lose 40-60 % of their density.In a pure (classic) TE, hair sheds 6-10 weeks after the illness and continues for another 4-7 months. Hair grows back by one year.Be sure to see a dermatogist for evaluation if shedding does not improve.

the amount of hair lost from TE, varies in each and every person. You need to see a doctor to evaluate the hair loss and to have it quantified. 

you can suffer from temporary hair loss from a prolonged illness. The amount of hair loss is not definite and may vary in each individual. However due to the temporary nature of hair loss, the lost hair may return. It is s good idea to speak to a hair restoration specialist to find ways to slow down the progression of your hair loss.