A coleta de sangue começa agora.

Because coleta is a feminine singular noun in Portuguese, so it normally takes the feminine singular definite article a.

• a coleta = the collection
• o exame = the exam/test

In this sentence, a coleta de sangue is the whole subject, so a is like the in English.

In a medical or hospital context, using the article here sounds natural. Dropping it would usually sound less standard or more like a headline.

Because de sangue here expresses the type or purpose of the collection: it means blood collection in a general sense, not the collection of a specific blood.

Compare:

• coleta de sangue = blood collection / blood draw
• coleta do sangue = the collection of the blood

The version with do would usually suggest some specific blood already identified in the conversation, which is not the normal way to say this in a routine medical context.

Yes. Coleta is a common and standard Brazilian Portuguese noun meaning collection or gathering, and in healthcare it is very commonly used for taking samples.

Examples:

• coleta de sangue = blood draw / blood sample collection
• coleta de urina = urine sample collection
• coleta de material = sample collection

In Brazil, coleta de sangue sounds normal and professional in hospitals, labs, and clinics.

Because começa is the conjugated form of the verb começar.

• começar = infinitive, to begin
• começa = begins / starts

Here the subject is a coleta de sangue, which is third person singular, so the verb must match it:

• A coleta de sangue começa agora.

This is the same kind of change you see in English:

• to start
• it starts

The ç in Portuguese shows that the c is pronounced like an s sound before a, o, or u.

So:

• começa is pronounced roughly like ko-MEH-sa
• without the cedilla, comeca would suggest a hard k sound before a, which would be wrong

This happens in many Portuguese words:

• começar
• coração
• açúcar

So the cedilla is there to preserve the correct pronunciation.

Yes. Começa is in the present indicative, and Portuguese often uses the simple present for actions that are starting now or are part of an announcement.

So começa agora is a very natural way to say that something starts now.

Portuguese does not always need a progressive form like English does. In this context:

• A coleta de sangue começa agora. = standard, natural announcement
• A coleta de sangue está começando agora. = also possible, but a little more focused on the action being in progress

In announcements, schedules, procedures, and instructions, the simple present is extremely common.

Yes, you could. It is grammatical and understandable.

The difference is mainly one of style and focus:

• começa agora = starts now, simple and direct
• está começando agora = is starting now, emphasizes the beginning as it happens

In a clinic or lab announcement, começa agora often sounds more natural and concise.

Yes, agora can move around, but the end position is very natural.

Common possibilities:

• A coleta de sangue começa agora.
• Agora, a coleta de sangue começa.
• A coleta de sangue agora começa. (possible, but less common and often more marked)

Putting agora at the end is the most neutral and natural choice here. It gives the sentence a clear flow: subject + verb + time expression.

It sounds neutral to formal and very appropriate in a medical setting.

You might hear it:

• in a clinic
• in a hospital
• in a laboratory
• in an announcement to patients

It is not slangy or overly casual. It sounds professional and standard Brazilian Portuguese.

Not exactly.

• coleta de sangue = the act of drawing or collecting blood
• exame de sangue = blood test

So if someone says:

• A coleta de sangue começa agora, they mean the blood draw itself is starting now.
• O exame de sangue começa agora would sound less natural if they mean the actual needle-and-sample procedure, because exame refers more to the test as a whole.

In many real situations, learners confuse these two, so it is useful to keep them separate.

A helpful approximate pronunciation is:

ah ko-LEH-tah djee SANG-gwee ko-MEH-sah ah-GOH-rah

A few notes:

• coleta has stress on le: co-LE-ta
• de often sounds like djee in many Brazilian accents before a consonant? Actually before s it is often closer to dji or ji depending on region, but learners can safely start with a light de
• sangue is roughly SANG-gwee
• começa has stress on me: co-ME-ça
• agora is usually a-GO-ra

The most important stresses are:

• coLEta
• sanGUE
• coMEça
• aGOra

Sometimes, but coleta de sangue is the standard and safest choice.

Possible alternatives depend on context:

• tirar sangue = to draw blood, more everyday and verbal
• retirada de sangue = removal of blood, possible but less standard in many routine medical contexts
• colher sangue / colheita de sangue = more associated with European Portuguese or more technical/literary usage, less typical in everyday Brazilian Portuguese

So for Brazilian Portuguese, coleta de sangue is the most natural expression to learn first.