Does one go bald in telogen effluvium?

TE can cause significant thinning 

Telogen effluvium is a hair shedding conditions whereby affected individuals lose more hair on a daily basis than they once did. It's important to understand that one's hair can go very thin but one NEVER loses all hair.

Why does one never lose all hair in TE?

Patients with telogen effluvium never go completely bald because not all the hairs on the scalp are converted to telogen hairs. A biopsy of TE will often show an increase in the proportion of telogen follicles above the typically expected level of 6-13 %. If the proportion of telogen follicles above 15% this suggests TE. However, if it's above 25%, this is a more definitive feature. One must keep in mind that a biopsy showed 25 % telogen hairs means that 75 % of hairs are anagen and growing well rooted in the scalp. There are never 100 % of the hairs in telogen phase in a patient with telogen effluvium and never 100 % of hairs in telogen phase in a biopsy from telogen effluvium. Therefore, one never loses all their hair.  However, that said, an individual with TE can have significant thinning and may even feel that they have lost 70 % or more of their hair. some telogen effluviums are mild but others are severe. In more severe cases, a wig or scarf may be used short term by the patient. 

What if a patient does bald in TE?

If one loses all hair and is absolutely certain they have a telogen effluvium, it is likely that is also something else going on as well. In other words, another diagnosis is present in addition to the TE. For example, if one ALREADY has genetic hair loss (or some other hair loss condition) to start with the thinning with a TE can be very, very noticeable sometimes.  In such a situation, it is both conditions that are contributing to thinning not just the TE.