Ho preso la pillola, anzi ne ho presa mezza, perché mi sentivo già meglio.

Because the two parts follow two slightly different patterns.

• In ho preso la pillola, the object la pillola comes after the verb, so the past participle usually stays in its basic form: preso.
• In ne ho presa mezza, the object is represented by ne before the auxiliary, and Italian often makes the participle agree with the thing being referred to. Since the understood noun is pillola, which is feminine singular, you get presa.

So the change from preso to presa is about agreement, not a change of tense or meaning.

Here ne means something like of it or from it.

It refers back to la pillola and is used because the speaker is talking about a part/quantity of that thing:

• ne ho presa mezza = I took half of it

This is a very common use of ne in Italian with quantities:

• ne ho preso un po’ = I took a little of it
• ne voglio due = I want two of them
• ne ho letti tre = I read three of them

So ne is the natural pronoun when English would often use of it / of them or sometimes no extra word at all.

Because mezza agrees with the noun it refers to, which is pillola.

• pillola is feminine singular
• so half becomes mezza

The full version would be:

• ne ho presa mezza pillola

But since pillola is already understood, Italian leaves it out and just says mezza.

Compare:

• mezzo bicchiere = half a glass
• mezza pillola = half a pill

Anzi is used to correct or refine what was just said.

Here the speaker first says:

• Ho preso la pillola = I took the pill

Then immediately adjusts that statement:

• anzi ne ho presa mezza = actually, rather, I took half of it

So anzi here means something like:

• actually
• rather
• or rather
• better said

It is often used when a speaker wants to replace a previous statement with a more accurate one.

Because sentirsi means to feel in the sense of one’s condition or state.

• mi sentivo meglio = I was feeling better

Without mi, sentivo usually means I heard or I felt/sensed something:

• sentivo un rumore = I heard a noise
• sentivo freddo = I felt cold

But when talking about how you yourself are feeling overall, Italian very often uses sentirsi:

• mi sento bene = I feel well
• si sente male = he/she feels unwell

So mi is not optional here; it is part of the verb sentirsi.

The imperfect sentivo presents the feeling as an ongoing background state.

The idea is:

• I took the pill — or rather half of it —
• because I was already feeling better

So mi sentivo già meglio describes the condition the speaker was in at that moment.

If you used mi sono sentito/a, it would sound more like a completed event: I felt better at a particular point. That is possible in some contexts, but here the imperfect is more natural because it gives the background reason for taking only half.

Già means already.

So:

• meglio = better
• già meglio = already better

It shows that the improvement had started before the action of taking the pill.

Also, meglio is the normal Italian word for better here. Standard Italian says:

• sto meglio = I feel better

not più bene.

Because the conjunction perché is normally spelled with an accent in modern Italian.

In this sentence it means because:

• perché mi sentivo già meglio = because I was already feeling better

The accent is part of the normal spelling. You should write perché, not perche.

The same word can also mean why in a question:

• Perché hai preso solo mezza pillola? = Why did you take only half a pill?

Yes. Both are correct, but they are not framed in exactly the same way.

• Ho preso mezza pillola is the straightforward full version.
• Ne ho presa mezza is more linked to the previously mentioned pillola and emphasizes the quantity taken from it.

In this sentence, ne ho presa mezza sounds especially natural after anzi, because the speaker is correcting the first statement and focusing on the amount:

• Ho preso la pillola — anzi, ne ho presa mezza

So the version with ne is very idiomatic here.

You may hear both, especially in speech.

• ne ho presa mezza shows agreement with pillola and is the more careful, standard form.
• ne ho preso mezza is also heard in everyday spoken Italian.

So for a learner, presa is the safer form to produce here, especially in writing, because it clearly matches the feminine singular noun understood in the sentence.

Because the repetition helps show the correction clearly.

The pattern is:

• first statement: Ho preso la pillola
• correction: anzi ne ho presa mezza

Italian often repeats the verb in this kind of self-correction, especially after anzi. It sounds natural because the second part is not just adding information; it is replacing the first statement with a more precise one.

So the repetition is not awkward here. It is part of how the correction is structured.