Learn French: Il fallait prendre des médicaments pour cette maladie. - One had to take medication for this illness.

In the expression il fallait, the il is impersonal. It doesn't refer to a specific person, much like the "it" in "it was raining." Il fallait literally means "it was necessary," which we often translate into English as "one had to," "you had to," or "people had to" depending on the context.

Why isn't the verb "prendre" conjugated here?

When you want to say "it was necessary to do something", you just place the second verb directly in its dictionary form (the infinitive) right after il fallait. So, il fallait + prendre simply means "it was necessary to take."

The English translation says "medication" (singular). Why does the French use the plural "des médicaments"?

In English, "medication" or "medicine" is usually an uncountable concept, so we use the singular. In French, un médicament is a countable thing (like a pill, a syrup, or a specific treatment). When talking about taking medication in general, French uses the plural des médicaments (literally "some medicines").

Why is it "cette maladie" and not "ce maladie"?

The word maladie (illness/disease) is a feminine noun. To say "this" or "that" before a feminine noun, you must use cette. If the noun were masculine, you would use ce (or cet if it started with a vowel).