O médico disse que a infeção já não é grave, desde que eu tome o antibiótico até ao fim.

Já não means no longer or not anymore.

So já não é grave means that the infection used to be serious before, but now it isn’t.

In Portuguese, já often adds the idea of a change in state:

• já é grave = it is serious now / already serious
• já não é grave = it is no longer serious

The order matters: já não normally comes before the verb.

Because desde que here means provided that / as long as, and this use normally requires the subjunctive in Portuguese.

So:

• eu tomo = indicative, a normal statement of fact
• eu tome = present subjunctive, used after certain expressions of condition, doubt, desire, etc.

In this sentence, the idea is conditional: the infection is no longer serious provided that I take the antibiotic until the end.

That is why tome is correct.

No. In this sentence, desde que means provided that or as long as.

That is a very important point, because desde que can have different meanings depending on context.

Here:

• desde que eu tome o antibiótico até ao fim = provided that I take the antibiotic until the end

In other contexts, desde que can be more time-related, but in this sentence it is clearly conditional, not temporal.

It is not strictly necessary, because Portuguese verb endings often show the subject.

So you could say:

• desde que tome o antibiótico até ao fim

However, eu is often added for clarity, contrast, or simply because the speaker wants to make the subject explicit.

Here it helps make it clear that I am the one who must take the antibiotic.

Also, tome can be the same form for eu, ele, ela, você, so adding eu removes any possible ambiguity.

Portuguese does not always shift tenses back the way English often does in reported speech.

So after disse que, Portuguese can keep the present tense if the information is still true now.

That is what happens here:

• O médico disse que a infeção já não é grave
  = the doctor said that the infection is no longer serious, and this is still true now

If you said não era grave, that would sound more like you are reporting what the doctor said at that time, without necessarily presenting it as still true now.

So é fits well because the condition is understood as current.

Yes. In Portuguese, tomar is the normal verb for taking medicine.

So:

• tomar um comprimido = to take a tablet
• tomar antibióticos = to take antibiotics
• tomar o antibiótico = to take the antibiotic

This is a very common use of tomar in both European and Brazilian Portuguese.

Até ao fim means until the end.

In this medical context, it means the person must continue taking the antibiotic for the full course, not stop early just because they feel better.

So it carries the practical idea of:

• finish all the medication
• complete the treatment

That is a very common expression in Portuguese.

Ao is the contraction of a + o.

So:

• a + o = ao

In European Portuguese, até ao fim is the natural standard form here.

You may sometimes see até o fim, but até ao fim is especially common and natural in Portugal.

Infeção is the current official spelling under the modern Portuguese spelling rules.

The older spelling was infecção.

In Portugal, because the c is not pronounced in this word, the reformed spelling removes it:

• old: infecção
• current official: infeção

You may still come across the older spelling, especially in older texts or from people who prefer pre-reform spelling, but infeção is the standard modern form.

Portuguese uses definite articles more often than English.

Here they sound natural because the speaker is referring to specific things already known in the situation:

• o médico = the doctor involved in this case
• a infeção = the infection being discussed
• o antibiótico = the antibiotic prescribed or being taken

English sometimes omits articles where Portuguese keeps them, so this is something learners often need to get used to.

Because grave is an adjective with the same form in masculine and feminine singular.

So:

• o problema é grave
• a infeção é grave

The adjective does agree in number, though:

• o problema é grave
• os problemas são graves
• a infeção é grave
• as infeções são graves

So in this sentence, grave already agrees correctly with a infeção.

Because the two ques do different jobs.

1. disse que
   Here que introduces a reported statement:

   • He said that...

2. desde que
   Here que is part of the fixed expression desde que, meaning:

   • provided that / as long as

So this is completely normal Portuguese. Even though the same word appears twice, it is not repetitive in a bad way; it is just doing two different grammatical jobs.