Which is correct?

The medical term and spelling is Hemorrhoid.

The most common misspelling is to spell it like it sounds, therefore: Hemroid

Here’s what I found on dictionary.com

<—- excerpt—->
hem·or·rhoid
[hem-uh-roid, hem-roid]
–noun
Usually, hemorrhoids.
Pathology. an abnormally enlarged vein mainly due to a persistent increase in venous pressure, occurring inside the anal sphincter of the rectum and beneath the mucous membrane
(internal hemorrhoid) or outside the anal sphincter and beneath the surface of the anal skin (external hemorrhoid).
Also called pile.

<—- end of excerpt—->

(now you know!)

Here’s some other spellings I came across on various forums and blog posts.

Hemorhoid, Hemaroid, Hemmorrhoid, Hemroyd, Hemerroid, Hemmorrhoid, Hemhroid.

It really doesn’t matter how you spell it, it’s still a pain in the ass! (pun: sorry!)