It is generally safe to take Mucinex (specifically, the regular Mucinex containing only guaifenesin) and DayQuil together since their active ingredients do not typically overlap or interact. However, caution is needed if using Mucinex DM, which contains dextromethorphan, because DayQuil also contains dextromethorphan. Taking both together could result in too much of this cough suppressant and increase side effects like dizziness and drowsiness. Also, since DayQuil contains acetaminophen, care should be taken not to exceed the recommended acetaminophen dose if other medications containing it are being used. It is advisable to space out the doses of Mucinex and DayQuil by a few hours for best effectiveness and to reduce side effects. In summary:

• Mucinex (guaifenesin-only) and DayQuil can be taken together safely.
• Avoid combining DayQuil with Mucinex DM (which contains dextromethorphan).
• Do not exceed acetaminophen dosage limits in DayQuil.
• Consider spacing doses by several hours.
• Watch for side effects such as dizziness, nausea, or stomach upset.

If uncertain or taking other medications, consulting a healthcare provider or pharmacist is recommended before combining these medicines.