Senti tontura, então me hidratei.

Both senti and hidratei are in the preterite (also called the simple past) in Portuguese.

• senti = I felt
• hidratei = I hydrated

This tense is used for completed actions in the past. In this sentence, the speaker is describing two finished actions:

1. Senti tontura = I felt dizzy / I felt dizziness.
2. então me hidratei = so I hydrated myself.

So the sentence narrates a sequence of past events.

Portuguese often omits subject pronouns when the verb already makes the subject clear.

Here, senti clearly means I felt, and hidratei clearly means I hydrated, so eu is not necessary.

You could say:

• Eu senti tontura, então me hidratei.

But in natural Brazilian Portuguese, leaving out eu is very common unless you want emphasis or contrast.

For example:

• Eu senti tontura, mas ela não sentiu nada.
  = I felt dizzy, but she didn’t feel anything.

Tontura is a noun, while tonto/tonta is an adjective.

• tontura = dizziness
• tonto / tonta = dizzy

So:

• Senti tontura literally means I felt dizziness
• Fiquei tonto/tonta means I became dizzy
• Estava tonto/tonta means I was dizzy

All of these can be natural, but they are structured differently.

Examples:

• Senti tontura depois do treino.
• Fiquei tonta quando levantei rápido.
• Eu estava tonto o dia inteiro.

If the speaker is female, she might say fiquei tonta; if male, fiquei tonto. But tontura works the same for anyone.

Both are possible, but they mean slightly different things.

• Senti tontura = I felt dizzy / I felt dizziness
  This is very natural and general.
• Senti uma tontura = I felt a spell of dizziness / a dizziness
  This can sound a bit more specific, like one episode.

Portuguese often leaves out the article with symptoms or conditions in expressions like this.

Compare:

• Senti fome. = I felt hungry.
• Senti medo. = I felt afraid / I felt fear.
• Senti tontura. = I felt dizzy.

So senti tontura is very normal.

Here, então means so, then, or therefore.

It connects the first idea to the second:

• Senti tontura, então me hidratei.
• I felt dizzy, so I hydrated myself.

It shows a result or reaction: because the speaker felt dizzy, they drank water or otherwise hydrated.

In conversation, então is extremely common and can have several uses depending on context, but in this sentence it works as a connector meaning so.

Because hidratar-se is commonly used as a pronominal verb when it means to hydrate oneself.

• me hidratei = I hydrated myself
• se hidratou = he/she hydrated himself/herself
• nos hidratamos = we hydrated ourselves

In everyday Brazilian Portuguese, saying me hidratei is very natural when you mean you drank water or replaced fluids.

If you say just hidratei, people may expect a direct object:

• Hidratei a pele. = I moisturized/hydrated the skin.
• Hidratei o cabelo. = I hydrated/moisturized the hair.

So me hidratei makes it clear that the speaker is talking about their own body.

Yes, grammatically it is correct, but in Brazilian Portuguese, me hidratei sounds much more natural in everyday speech.

Compare:

• me hidratei = common in Brazil
• hidratei-me = correct, but more formal or more typical of written/literary style

Brazilian Portuguese strongly prefers placing object pronouns before the verb in many everyday contexts, especially in speech.

So for a learner focused on Brazil, me hidratei is the form to use.

Usually, yes, or at least that the speaker took care of their hydration.

Depending on context, it may mean:

• drank water
• drank electrolytes
• rehydrated after exercise, heat, illness, etc.

It does not always describe the exact method, but in normal conversation people will usually understand it as I drank fluids.

If you want to be more explicit, you could say:

• bebi água = I drank water
• fui beber água = I went to drink water
• me reidratei = I rehydrated myself

Yes, it is completely natural.

It sounds like a normal way to describe a symptom. A Brazilian speaker might also say:

• Fiquei tonto/tonta.
• Tive uma tontura.
• Comecei a sentir tontura.

These are all natural, but they are slightly different:

• Senti tontura = I felt dizziness / I felt dizzy
• Fiquei tonto/tonta = I got dizzy
• Tive uma tontura = I had a dizzy spell
• Comecei a sentir tontura = I started to feel dizzy

So the original sentence is very idiomatic.

The comma helps separate the two clauses:

• Senti tontura
• então me hidratei

This is similar to English punctuation in:

• I felt dizzy, so I hydrated myself.

In Portuguese, a comma before connectors like então is very common when linking two full ideas. It makes the sentence easier to read and sounds natural in writing.

Not as a direct replacement in the same style. That version sounds less natural for this simple statement.

The original sentence means:

• I felt dizzy, so I hydrated myself.

If you use porque, you are usually expressing because:

• Me hidratei porque senti tontura.
  = I hydrated myself because I felt dizzy.

That is also correct and natural, but the structure changes:

• então = so
• porque = because

So both can work, but they express the relationship from different angles.

This exact sentence would not change.

• Senti tontura, então me hidratei.

There is no adjective here that has masculine/feminine agreement, so the sentence is the same for a man or a woman.

If you used an adjective instead, then it would change:

• male: Fiquei tonto.
• female: Fiquei tonta.

But tontura is a noun, and hidratei does not change for gender.

hidratei is the first-person singular preterite form of hidratar.

The verb pattern is:

• hidratar
• eu hidratei
• você/ele/ela hidratou
• nós hidratamos
• eles/elas hidrataram

Many -ar verbs form the eu preterite with -ei:

• falar → falei
• tomar → tomei
• hidratar → hidratei

So -ei is a normal past-tense ending for I with -ar verbs.

In Brazilian Portuguese pronunciation, hidratei sounds roughly like ee-drah-TEY, though exact pronunciation varies by region.

Yes, depending on context.

Tontura can refer to:

• dizziness
• lightheadedness
• feeling faint or unsteady

So the best English translation depends on the situation. If the learner has already been shown one meaning, that is probably the intended one, but the Portuguese word can cover a range of similar sensations.