A tontura começou depois da coleta de sangue.

Because tontura is a feminine singular noun, and Portuguese often uses the definite article where English might not.

So:

• a tontura = the dizziness
• uma tontura = a dizziness / a dizzy spell

In Portuguese, it is very natural to say A tontura começou... even if English might simply say Dizziness started... or The dizziness started...

Tontura usually means dizziness, lightheadedness, or a dizzy feeling.

It is a general word for feeling unsteady or like your head is spinning. Depending on context, English could translate it as:

• dizziness
• lightheadedness
• feeling dizzy

A related word is vertigem, which is often closer to vertigo specifically.
So tontura is usually the broader, more everyday term.

Começou is the preterite form of começar (to begin / to start).

• começar = infinitive
• começou = started / began

This tense is used because the sentence refers to a completed event in the past: the dizziness started at a certain moment.

So:

• A tontura começou... = The dizziness started...

If you used the imperfect instead, such as começava, it would suggest an ongoing or habitual past action, which does not fit as well here.

Because depois by itself usually means later or afterward, but when it is followed by a noun, Portuguese normally uses depois de.

So:

• depois = later / afterward
• depois de
  • noun = after

Here the noun phrase is a coleta de sangue, so:

• depois de a coleta de sangue

But Portuguese normally contracts de + a into da:

• de + a = da

So the final form is:

• depois da coleta de sangue = after the blood draw / after the blood collection

Coleta de sangue literally means collection of blood, but in natural English it usually means:

• blood draw
• blood collection
• sometimes, depending on context, part of a blood test

It refers to the act of taking blood from someone, usually in a medical setting.

So in this sentence, depois da coleta de sangue means after the blood was drawn.

Because de sangue here describes the type or purpose of the collection.

• coleta de sangue = blood collection / collection of blood
• amostra de sangue = blood sample
• teste de sangue = blood test

Portuguese often uses de without an article in this kind of classification or descriptive phrase.

If you said do sangue, that would mean of the blood, referring to some specific blood already identified in context. That is not the idea here.

Yes. Após a coleta de sangue is correct and means the same thing.

Compare:

• depois da coleta de sangue = very common, natural, everyday
• após a coleta de sangue = also correct, slightly more formal or clinical

In medical or written contexts, após is especially common.

Yes, the given word order is very natural, but Portuguese allows some flexibility.

The original order is:

• A tontura = subject
• começou = verb
• depois da coleta de sangue = time expression

This is the most neutral structure.

You could also say:

• Depois da coleta de sangue, a tontura começou.

That is grammatically fine, but it sounds a bit more marked or literary. In everyday speech, the original version is more natural.

In Brazilian Portuguese, começou is pronounced roughly like ko-me-SOH, with the stress on the last syllable.

A few pronunciation notes:

• ç sounds like s
• ou in Brazilian Portuguese often sounds like oh
• the stress falls on çou

So:

• co-me-ÇOU
• approximately ko-me-SOH

It can do both, depending on context.

It may refer to:

• a general symptom: dizziness
• a specific episode or spell: a dizzy spell

For example:

• Estou com tontura. = I feel dizzy / I have dizziness.
• Tive uma tontura. = I had a dizzy spell.

In your sentence, A tontura começou... most naturally refers to the onset of the symptom.

Yes, very often.

A more personal version would be:

• Fiquei tonto depois da coleta de sangue. if the speaker is male
• Fiquei tonta depois da coleta de sangue. if the speaker is female

That means:

• I got dizzy after the blood draw
• I felt dizzy after the blood draw

The original sentence is a bit more impersonal and medical because it talks about the dizziness as a symptom.