A hemoglobina está baixa.

Here, a is the feminine singular definite article, meaning the.

So:

• a hemoglobina = the hemoglobin

In Portuguese, nouns usually take an article more often than in English, so using a here sounds natural.

Because hemoglobina is a feminine noun in Portuguese.

You can see that in two places:

• a hemoglobina → feminine article
• baixa → feminine form of the adjective

Many nouns ending in -a are feminine, and hemoglobina is one of them.

Portuguese has two main verbs for to be: ser and estar.

Here, está is used because this sentence describes a current condition or state:

• A hemoglobina está baixa. = the hemoglobin level is low right now / at this moment / in this test result

That is why estar sounds natural in medical contexts for lab values, symptoms, and temporary conditions.

Compare:

• está baixa = is low, currently
• é baixa = is low by nature / generally / as a characteristic

In this sentence, está is the normal choice.

Because adjectives in Portuguese usually agree with the noun they describe.

Since hemoglobina is:

• feminine
• singular

the adjective must also be:

• feminine
• singular

So:

• baixo = masculine singular
• baixa = feminine singular

That is why we say A hemoglobina está baixa.

Here, baixa means low.

In medical language, it refers to a level below normal. So in this sentence, it means the hemoglobin level is low.

The adjective baixo/baixa can mean different things depending on context, such as:

• low
• short
• low in volume
• down

But in this sentence, the meaning is clearly low.

Not literally, but that is often the idea in context.

Portuguese commonly says:

• A hemoglobina está baixa.

Even though in English we might naturally say:

• Hemoglobin is low
• Your hemoglobin level is low

So Portuguese often uses just hemoglobina, while English may add level if needed.

Yes, very important.

• está = is / is being (from estar)
• esta = this (feminine)

So:

• A hemoglobina está baixa. = correct
• A hemoglobina esta baixa. = missing the accent, and in standard writing that is incorrect

The accent also shows the correct stress: es-TÁ.

Usually, no. In a normal sentence like this, that sounds unnatural.

The natural form is:

• A hemoglobina está baixa.

Portuguese usually wants the article with this noun in this kind of statement.

If you add a possessive or other determiner, the structure changes, for example:

• Sua hemoglobina está baixa. = Your hemoglobin is low.

But by itself, Hemoglobina está baixa is not the normal way to say it.

Yes. That is perfectly natural.

• A hemoglobina está baixa. = The hemoglobin is low.
• A hemoglobina está muito baixa. = The hemoglobin is very low.

You can also hear:

• Sua hemoglobina está baixa.
• O nível de hemoglobina está baixo.

All of these are natural in medical contexts.

Yes, especially in a medical context.

A doctor, nurse, or patient might say:

• A hemoglobina está baixa.
• Sua hemoglobina está baixa.

This is a normal and natural sentence in Brazilian Portuguese when talking about blood test results.

A simple pronunciation guide is:

ah eh-moh-gloh-BEE-nah es-TAH BY-shah

A few notes:

• hemo- in Portuguese starts with a silent h
• globi sounds like gloh-BEE
• está is stressed on the last syllable
• baixa in Brazilian Portuguese sounds roughly like BY-shah

It follows a very common pattern:

article + noun + estar + adjective

So here:

• A = the
• hemoglobina = hemoglobin
• está = is
• baixa = low

This pattern is extremely useful for describing temporary conditions:

• A pressão está alta. = The blood pressure is high.
• A glicose está baixa. = The glucose is low.
• A temperatura está normal. = The temperature is normal.