I ate a little bit after taking miralax (polyethylene glycol). I take it in the morning and at night but have never eaten after taking the night dose. Will I be constipated now or will I be ok?

No change expected. You take MiraLAX (polyethylene glycol) and ate after taking it. No change is expected in your bowels by eating after the miralax (polyethylene glycol). Miralax (polyethylene glycol) works by holding onto water in your colon. This prevents the stool from becoming hard. If you eat it should not change the way MiraLAX (polyethylene glycol) works and you should have the regular bowel movent. See your doctor if you need MiraLAX (polyethylene glycol) all the time.
You'll be fine. Miralax (polyethylene glycol) just acts by attracting water into the colon and thus, into the stool. It really is not reliant on eating or not eating to work, so you will be just fine and should not be constipated because of your intake with the medicine.