My dosage of metoprolol ER has been reduced from 50mg to 25mg. Is it OK to cut the pill in half?

You're may both be right on this one! It's VERY unusual to be able to cut an extended-release pill. Generally, that releases all the medication at once because you lose the protective coating that is designed to provide the slow release. However, here's what I found through a pharmacist research article: Metoprolol Tartrate XL is delivered with tiny little beads inside the scored pill's protective covering which are each their own tiny delivery system. This is why they are scored and it's safe to cut them in half, even if it's the extended-release version. There are good articles on this which I tried to copy and paste here but I couldn't. However, just look that up. For that same reason, however, you cannot crush them.

To Metoprolol
From bestpup
Regardless of the dose never do you cut an ER medication in half. The ER before the Metoprolol means EXTENDED RELEASE.
By cutting the medication in half your body will breakdown the medication immediately rather than it's intended form which is extended release.
Best regards
bestpup

Any medication with the letter ER, XL, XT, etc. Stand for extended release and should never be broken, scored or not. It releases small amounts of the medication in your system over a 24 hour period and that is the way the doctor wants you to take it. To break the coating would give you the dose right away. It could over tax your body and leave you with out enough medication in your system for 24 hours.

I had the same question. I just called the pharmacist and was told it's ok to cut it. The rule seems to be it it's scored it's safe to cut it.

I do it all the time.
Hope you feel better

Never , cut, chew, split or break an ER (extended release) medication , doing so may cause undesirable side effects as it will release too much of the medication at once.