Learn Hardcore Croatian: Njena temperatura nije visoka, ali pije lijek. - Her temperature is not high, but she is taking medicine.

The subject is understood to be she, not the temperature. Croatian regularly drops subject pronouns when the verb form makes it clear. So pije = "she drinks/takes." If you want to make it explicit, you can say ali ona pije lijek.

Why is there a comma before ali?

Because ali (but) connects two independent clauses. Standard Croatian punctuation puts a comma before ali.

Is njena the best form here? I’ve seen njezina too.

Both njena and njezina mean her. In standard Croatian, njezin(a) is often preferred, but njen(a) is common and acceptable. So Njena temperatura... and Njezina temperatura... are both fine.

Why njena temperatura and not njene temperatura?

Agreement. Temperatura is feminine singular nominative, so the possessive must match: njena (fem. sg. nom.). njene is either feminine plural nominative or feminine singular genitive and doesn’t fit here.

Why nije visoka and not nije visoko?

Visoka agrees with temperatura (feminine singular). Visoko is neuter or an adverb ("highly"), so it would be incorrect here.

What tense/aspect is pije? How would I say "she took one dose of medicine"?

Pije is present tense, imperfective (from piti). For a single completed dose, use perfective popiti: Popila je lijek (she took/drank the medicine). For habitual taking, use uzimati: Uzima lijek svaki dan.

Does pije lijek literally mean "drinks medicine"? Do Croats say that even for pills?

Literally yes, but idiomatically it means "takes medicine," including pills. You’ll also hear:

uzimati/uzeti lijek (to take medicine)
popiti lijek (to take a dose/drink up the medicine) All are natural; popiti highlights a single completed act.

Why doesn’t lijek change form after pije? Isn’t that accusative?

It is accusative, but masculine inanimate nouns have the same form in nominative and accusative singular. So lijek (nom.) = lijek (acc.). Animate masculine nouns change (e.g., pas → psa).

How can I add the idea "still/anyway" to stress the contrast?

Use ipak: Njena temperatura nije visoka, ali ipak pije lijek (…but she still takes medicine).

Is there a more idiomatic way to express possession with body states?

Yes. Croatian often uses a dative pronoun:

Temperatura joj nije visoka, ali pije lijek. (literally "The temperature to her is not high…")
This sounds very natural.

Can I include the pronoun ona in the second clause?

Yes, for emphasis or clarity: … ali ona pije lijek. Normally Croatian drops subject pronouns.

What’s the difference between ali and no?

Both mean but. No is a bit more formal/literary and can feel stronger: … nije visoka, no pije lijek.

How do I say "She doesn’t have a high temperature" with imati/nemati?

Nema visoku temperaturu, ali pije lijek. Note the accusative visoku temperaturu after imati/nemati.

If I replace lijek with a pronoun, where does it go?

Use the clitic ga and put it in second position in the clause: … ali ga pije. After a connector like ali, clitics come right after it.

How do I pronounce nj, lj, and the ije sequence?

nj (as in njena) is one sound, like Spanish ñ.
lj (as in lijek) is a palatal L, similar to Italian gli.
ije is pronounced as two vowels (i + je); don’t reduce it to a simple e.

Is medicina a good word for "medicine" (a drug)?

No. Medicina is the field of medicine. For a drug/medication, use lijek (plural lijekovi). For a liquid medicine, sirup. For a pill, tableta.

Is the word order Ali lijek pije possible?

Grammatically yes, but it’s marked and emphasizes lijek ("It’s the medicine that she’s taking"). Neutral order is … ali pije lijek.