If you want to ask directly, in the United States we use the verb "to fail" (to not pass or to not succeed at an exam or class) rather than "to lose." You can either pass a class or an exam, or fail it.
If you don't understand the course material at all or if you miss the final, you may fail the class. Then, if it is a required class, you'll have to repeat it until you pass.
So, you might ask,
What happens if you fail the chemistry exam? Can you still pass the class?
Did you pass the chemistry final? (you can say "final exam" or just "final")
Do you think you're going to pass the class?
Are you going to have to repeat the class?
Are you going to have to repeat chemistry next term/semester/year?
Marc thinks he'll have to repeat first-semester chemistry. He studied really hard, but still failed the final.
Tim, in his answer, has some good points about the appropriateness of the question, and how to ask it less directly. But if you want to ask the question the way you posed it, you can use the above.