To handle missing data:

Blank represents character missing in SAS.
Period or (.) represents numeric missing in SAS.

Data mh3;
Infile cards;
Input pid visit $ dose;
cards;
01 visit 1 0.05
102 visit 0.1
103 vusut1 0.05
101 . 0.05
102 visit2 .
103 visit2 0.15
;
Proc print data=mh3;
Run;