If you're vomiting blood frequently, call an ambulance or have a nearby internist make a house call.
Literal
Frequently vomit-blood do case [topic-は], ambulance [object-を] call [or-か], nearby internal-medicine-doctor [to-に] house-call [object-を] have-do.
Medical emergency advice. 吐血 (vomiting blood) is a medical term. 往診してもらう uses ~てもらう (have someone do something for you) with 往診 (house call). ~か links two alternatives. ひんぱんに (frequently) is written in hiragana rather than the kanji 頻繁に, which is common in health guides aimed at general audiences.