How should I respond to this email?

I’d say “Hello, Mr. _____, Yes, I received the email and I am planning to go to ______ to do the drug screening today, around ______ pm. Thank you so much for following up. I look forward to hearing from you.

The request for drug screening will have a MUST BE DONE BY date.
Just make sure you get there before it expires.
Reply to the email from the employer as an opportunity to let them know how much you want the job and will get the screening completed today. Don’t elaborate on the missed email for a few hours. It really is not relevant as long as you get the test done in time.

People know that not everyone checks their emails frequently. I know people that check it once at the end of the day. What I’m trying to get across is that I don’t think it’s a big deal to not have responded yet. I strongly advise that you do what @jca2 suggested above. Don’t over-explain, just write what’s in the above post. Good luck!

@jca2 Has the best thing to do. Just say ” Hello Mr.__, I got the email a little late but I am planing on doing the drug screening today around something PM. Thanks for the follow up and I look forward to hearing back from you.” You can use this or @jca2‘s or both. Make sure you do it before it expires.