Research paper from University of California claims 70% of Covid-19 patients loose their sense of smell but only 50% notice this on their own.

https://medicalxpress.com/news/2020-11-covid-loss-uncovered-team.html

Sample quote

People with colds and flus report losing their senses of smell and taste, too, but COVID-19 is not the cold or flu, and sufferers don't usually have congested noses.
...snip...
"People don't tend to have the same awareness of their sense of smell as of other senses," Hannum said. "We don't always have the language to describe it. People often mistake sense of smell for sense of taste."

End quote