Om du är förkyld, borde du vila hemma och ta hostmedicin i kväll.

Because Swedish uses verb-second (V2) word order in main clauses.

The sentence starts with the subordinate clause Om du är förkyld. After that, the main clause begins, and in a Swedish main clause the finite verb usually comes in the second position. So you get:

• Om du är förkyld, borde du ...

not

• Om du är förkyld, du borde ...

This is very common in Swedish:

• I dag går jag till jobbet.
• När han kommer, äter vi.
• Om det regnar, stannar jag hemma.

So after a fronted phrase or clause, Swedish usually puts the verb before the subject in the main clause.

Here om means if.

So:

• Om du är förkyld = If you have a cold / If you are congested

It introduces a condition, just like English if.

A few more examples:

• Om du vill, kan vi gå nu. = If you want, we can go now.
• Om det regnar, stannar vi hemma. = If it rains, we’re staying home.

Swedish often expresses this idea with an adjective:

• vara förkyld = to have a cold / to be suffering from a cold

So although English usually says have a cold, Swedish very naturally says be colded/congested, so to speak.

Both of these are possible:

• Jag är förkyld. = I have a cold.
• Jag har en förkylning. = I have a cold.

But jag är förkyld is extremely common and natural in everyday Swedish.

Förkyld means having a cold, congested, or down with a cold.

It is an adjective, so it changes for gender/number if needed:

• Jag är förkyld.
• Hon är förkyld.
• Barnet är förkylt.
• Vi är förkylda.

A learner should especially notice that Swedish uses it as an adjective after är.

Borde means should / ought to.

It gives advice or a recommendation, not a strict command.

So:

• Du borde vila hemma. = You should rest at home.

This is softer than something like:

• Du måste vila hemma. = You must rest at home.

And it is different from:

• Du ska vila hemma. = You are to rest at home / you will rest at home / you should rest at home, depending on context

So borde is a good word for advice, especially in health-related sentences.

In Swedish, uncountable or general substances often appear without an article, just like English sometimes does.

So:

• ta hostmedicin = take cough medicine

This is similar to:

• dricka vatten = drink water
• ta medicin = take medicine
• äta frukt = eat fruit

If you were talking about a specific medicine, you might make it more specific in some other way, but in this sentence hostmedicin is being used in a general sense.

Yes, ta hostmedicin is natural and idiomatic Swedish.

Swedish often uses ta with medicines:

• ta medicin = take medicine
• ta en tablett = take a tablet
• ta hostmedicin = take cough medicine

Even if the medicine is liquid, ta is still very common. In some contexts you might also hear more specific verbs, but ta is the normal general choice.

Hemma means at home, while hem means home in the sense of to home / homeward.

So:

• vila hemma = rest at home
• gå hem = go home

Compare:

• Jag är hemma. = I am at home.
• Jag går hem. = I am going home.

In your sentence, the meaning is location, not movement, so hemma is correct.

I kväll means this evening / tonight.

Yes, it is very common to also write it as one word:

• i kväll
• ikväll

Both are accepted in modern Swedish. The one-word spelling ikväll is very common in everyday writing.

Similar forms include:

• i dag / idag
• i morgon / imorgon

The comma separates the introductory conditional clause from the main clause:

• Om du är förkyld, borde du vila hemma ...

In Swedish, commas after short introductory clauses are often a style choice more than a strict necessity, especially in modern writing. So you may also see:

• Om du är förkyld borde du vila hemma ...

Both can be acceptable, depending on style and clarity. The comma can make the sentence easier to read.

Yes, but only if the sentence order changes.

If the main clause comes first, then normal word order is:

• Du borde vila hemma och ta hostmedicin i kväll om du är förkyld.

That is because in a normal Swedish main clause, the subject often comes before the verb:

• du borde

But if the sentence starts with Om du är förkyld, then the main clause follows V2 order:

• borde du

So both are possible, but the word order depends on what comes first.

It most directly means rest at home, but in natural English it can easily imply stay home and rest.

• vila = rest
• hemma = at home

So the Swedish focuses on the resting, while also stating where that rest should happen. In context, especially with illness, it naturally suggests not going out, not going to work or school, and taking it easy at home.

Yes, but borde is usually more common and natural in everyday speech.

• Du bör vila hemma. = You ought to rest at home.
• Du borde vila hemma. = You should rest at home.

Bör can sound a little more formal, written, or official. Borde is often the more conversational choice when giving ordinary advice.