Shall I take Pepcid every day or just when I need (or think I'm going to need) it?

Are you just taking Pepcid for heartburn? Then you can take it as needed. The general dosing guideline is given below.

* To treat duodenal ulcers:

o Older adults, adults, and teenagers—40 milligrams (mg) once a day at bedtime. Some people may take 20 mg two times day.
o Children—Dose must be determined by your doctor.

* To prevent duodenal ulcers:

o Older adults, adults, and teenagers—20 mg once a day at bedtime.
o Children—Dose must be determined by your doctor.

* To treat gastric ulcers:

o Older adults, adults, and teenagers—40 mg once a day at bedtime.
o Children—Dose must be determined by your doctor.

* To treat heartburn, acid indigestion, and sour stomach:

o Adults and teenagers—10 mg with water when symptoms start. The dose may be repeated once in twenty-four hours. Do not take more than 20 mg in twenty-four hours.
o Children—Dose must be determined by your doctor.

* To prevent heartburn, acid indigestion, and sour stomach:

o Adults and teenagers—10 mg taken one hour before eating a meal you expect to cause symptoms. The dose may be repeated once in twenty-four hours. Do not take more than 20 mg in twenty-four hours.
o Children—Dose must be determined by your doctor.

* To treat conditions in which the stomach produces too much acid:

o Older adults, adults, and children—20 mg every six hours. Your doctor may change the dose if needed.
o Children—Dose must be determined by your doctor.

* To treat gastroesophageal reflux disease:

o Older adults, adults, and teenagers—20 mg two times a day, usually for up to 6 weeks.
o Children weighing more than 10 kg (22 pounds)—1 to 2 mg per kilogram (kg) (0.5 to 0.9 mg per pound) of body weight a day divided into two doses.
o Children weighing less than 10 kg (22 pounds)—1 to 2 mg per kg (0.5 to 0.9 mg per pound) of body weight a day, divided into three doses.

https://www.drugs.com/cons/pepcid.html

Hope this helps.