The answer to the question in the title of your post (
Is 3.7 hv?) is:
No. 3.7V is the standard voltage of all unmodified e-cigs (as well as a great many
mods). 5V, 6V, and 7.4V are example of HV (high-voltage).
The answer to the question in the body of your post (
Can you vape Nhaler hv juice on it?) is:
Yes. I'm not sure what else NHaler may do to it (Drew says that it is a "thicker liquid"), but
I like it because it (and his Lung Juice) are his only 12mg e-liquid, which is
my comfortable level, even for 3.7V vaping.
Many vapers are comfortable with his 24mg Nhale/Xhale e-liquid at 3.7V. But higher voltages "burn" the liquid faster, delivering the vapor, flavor, and the nicotine more quickly and intensely ... so 12mg works for them at those higher voltages.