Is there a comma after therefore?

You generally don't use a comma after "therefore" unless it's followed by a dependent clause.

Here's a breakdown:

No comma:

* Therefore, I will stay home.

* She is tired. Therefore, she will go to bed early.

Comma:

* Therefore, because it is raining, we will stay inside.

* Therefore, if you are feeling unwell, you should see a doctor.

In short, use a comma after "therefore" when it introduces a dependent clause. A dependent clause is a group of words that cannot stand alone as a complete sentence.