It's important to try not to miss a dose of Toprol-XL. This is because this medication works best when there's a constant amount of medication in your system. If you do miss a dose, take it as soon as you remember.If it is almost time for your next dose , skip the missed dose and return to your regular schedule. Don't take extra medication or double up on doses to make up for any that you missed. Talk to your doctor if you're concerned about missing a dose of Toprol-XL.