question about `su` and `su -l`

What is the the best way to check someone if he is in full root mode "su -l" or not like "su" in a Slackware system?

thank you.

EDIT:EXAMPLE Code:Thu Apr-4 10:06:59pm)-(CPU 0.8%:0:Net 16)-(omen:~)-(66M:158)
> id
uid=1000(omen) gid=100(users) groups=100(users),7(lp),10(wheel),17(audio),18(video),19(cdrom),71(input),83(plugdev),84(power),86(netdev),93(scanner),281(docker),996(vboxusers)
(Thu Apr-4 10:07:02pm)-(CPU 0.8%:0:Net 16)-(omen:~)-(66M:158)
> su
Password:
(Thu Apr-4 10:07:02pm)-(CPU 0.8%:0:Net 16)-(root:/home/omen)-(66M:158)
> id
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),17(audio)
(Thu Apr-4 10:07:02pm)-(CPU 0.8%:0:Net 16)-(root:/home/omen)-(66M:158)
> exit
exit
(Thu Apr-4 10:07:20pm)-(CPU 0.8%:0:Net 15)-(omen:~)-(66M:158)
> su -l
Password:

Think big.
Pollute the Mississippi.

root@omen64:~# id
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),17(audio)
root@omen64:~#su and su -l gives the same output.