If’ usually introduces conditional clauses. The same applies to other conditionals such as unless, should and in case which, however, perform other functions in different contexts.

Note that we can also convey the same idea of past event and present result by using type 3 conditional (if + past perfect, would've + past participle) in both clauses If he'd taken the medication ...

The most common mixed conditional combination is when we have a third conditional in the if-clause (if + past perfect) followed by a second conditional (would + infinitive) in the main clause.