Я пришёл на медосмотр натощак, поэтому после анализа крови сразу захотел есть.

Пришёл is the masculine singular past tense of прийти (to come / to arrive).

Because Russian past tense agrees with gender in the singular, Я пришёл tells you the speaker is male.

If the speaker were female, it would be:

• Я пришла на медосмотр натощак...

The same applies later in the sentence:

• захотел = masculine
• захотела = feminine

Russian often uses на with events, appointments, procedures, and activities that you go to.

So:

• идти на медосмотр = to go for a medical examination
• идти на работу = to go to work
• идти на приём = to go to an appointment

By contrast, в is more about going into a physical place:

• в больницу = to the hospital / into the hospital
• в кабинет = into the office/room

Here, the speaker is going for the purpose of a medical checkup, so на медосмотр is natural.

Медосмотр is short for медицинский осмотр and means medical examination, checkup, or medical screening.

It is a very common word in everyday Russian, especially in contexts like:

• routine workplace checkups
• school or university medical checks
• pre-employment exams
• official health screenings

So на медосмотр is a very normal collocation.

Натощак means on an empty stomach.

It is basically used like an adverb, so you do not need a preposition with it.

Examples:

• сдавать кровь натощак = to give blood on an empty stomach
• прийти натощак = to come on an empty stomach
• принимать лекарство натощак = to take medicine on an empty stomach

English speakers sometimes expect something like на пустой желудок, but the normal Russian word here is натощак.

The sentence has two parts:

1. Я пришёл на медосмотр натощак
2. поэтому после анализа крови сразу захотел есть

Поэтому means therefore / so / that’s why, and it connects the second clause to the first. In standard punctuation, a comma is used before it here.

So the structure is:

• statement
• comma
• result/consequence introduced by поэтому

This is because of case government.

1. После requires the genitive

So:

• после чего? = after what?
• анализ becomes анализа

2. Крови is also genitive

The phrase анализ крови means analysis/test of blood = blood test.

So:

• анализ крови = blood test
• после анализа крови = after the blood test

This is a very common Russian structure: noun + noun in the genitive.

Examples:

• стакан воды = a glass of water
• чашка чая = a cup of tea
• анализ крови = blood test

Russian usually prefers анализ крови rather than an adjective-based phrase here.

Both structure and meaning are very natural this way:

• анализ крови = blood test
• literally: analysis of blood

English often compresses this into one noun phrase (blood test), but Russian commonly uses a head noun plus a genitive noun.

So после анализа крови is exactly the normal way to say after the blood test.

Захотел есть literally means wanted to eat and very naturally expresses became hungry / felt like eating.

Russian often uses захотеть + infinitive to show the sudden appearance of a desire:

• захотел спать = got sleepy / wanted to sleep
• захотел пить = got thirsty / wanted to drink
• захотел есть = got hungry / wanted to eat

So this sentence focuses on the moment the desire appeared, especially because of сразу (immediately).

If you said был голоден, that would describe a state (was hungry) rather than the change into that state.

Both can mean to eat, but есть is the neutral, standard verb.

• есть = neutral, normal in most contexts
• кушать = often softer, more child-directed, polite, or stylistically marked

So in ordinary narration, especially from an adult speaker, захотел есть sounds more natural than захотел кушать.

Сразу means right away / immediately.

It emphasizes that after the blood test, the speaker felt hungry at once.

So:

• захотел есть = wanted to eat / got hungry
• сразу захотел есть = immediately wanted to eat / immediately got hungry

It helps show the consequence of having come натощак.

Yes, both are perfective past forms:

• прийти → пришёл
• захотеть → захотел

Perfective verbs are used here because the sentence presents completed or single events:

• he arrived for the checkup
• then he suddenly felt the desire to eat

This is very natural in storytelling: one completed event leads to another.

If you used imperfective forms, the meaning would shift and sound less like a simple sequence of events.

Yes, but the meaning changes slightly.

In the given sentence:

• после анализа крови = after the blood test / after the blood analysis

Other possible phrases:

• после сдачи крови = after giving blood
• после того, как сдал кровь = after I gave blood

These focus more directly on the act of giving blood, while после анализа крови points to the test as a medical procedure.

In everyday speech, people may use any of these depending on what they want to emphasize.

It is common and normal in everyday Russian, though it refers to a somewhat official or institutional situation.

You will often hear it in contexts like:

• work
• school
• clinics
• medical paperwork
• government or administrative procedures

It is not overly technical. A learner should definitely know it.

Yes, that is close in meaning, but grammatically the Russian says something slightly more like:

• I came to the medical checkup on an empty stomach, so after the blood test I immediately wanted to eat.

A very natural English rendering would be:

• I came to the checkup on an empty stomach, so right after the blood test I got hungry.
• I went for a medical checkup fasting, so right after the blood test I wanted to eat immediately.

The Russian захотел есть is often best translated idiomatically as got hungry in this context.