Learn Dutch: De arts onmiddellijk raadplegen indien de bijwerking ernstig is. - Consult the doctor immediately in the event that the side effect is severe.

Both words mean 'if', but indien is highly formal. It is often translated as 'in the event that' or 'provided that'. You will mostly see it in written Dutch, such as in legal texts, contracts, and medical leaflets like this one.

Does indien affect the word order?

Yes. Because indien is a subordinating conjunction (a linking word that introduces a dependent clause), it forces the verb in its part of the sentence to the very end. That is why the verb is comes right at the end, after ernstig.

Why does the first part of the sentence use the full dictionary verb raadplegen (to consult) instead of a command like raadpleeg?

Using the infinitive (the full, un-conjugated verb) is a common way to give impersonal, general instructions in Dutch. You will often see this on packaging, user manuals, and public signs where the rule is not directed at one specific person.

Why is raadplegen placed after de arts onmiddellijk? Shouldn't verbs come first in a command?

In a normal command, the verb does come first (for example: Raadpleeg onmiddellijk de arts). However, when you use the infinitive form to give an impersonal instruction, that infinitive verb gets pushed to the very end of its clause.