Q. Does it matter if I miss taking a dose of an antibiotic?

If the directions call for taking one pill every six hours, do I have to take the pills exactly six hours apart?

For me, this would mean staying up late and also setting my alarm to get up early.

A. In general, you should follow the directions on your prescription.

But please don't hesitate to ask your doctor or pharmacist whether you can vary your dosing schedule somewhat to make it more convenient for you.

Most medicines work best when their level in your bloodstream is fairly steady. Your levels of medication shouldn't get too high, which may cause harmful effects; on the other hand, they shouldn't get too low, which may result in reduced effectiveness.

Luckily, however, most medicines aren't so critical that being late or missing a dose would lead to serious problems. Even for a drug like zidovudine (AZT), which is used to treat AIDS, the dose is every four hours while awake and not around the clock.

As a rule, if you miss a dose of an antibiotic, you can take it as soon as you realize you've forgotten. In many cases, you can double up on the next dose safely.

But be sure to check with your doctor, pharmacist or at the very least a book on prescription drugs to see if it's safe to do so. Books for the public about prescription drugs often have advice on what to do if you miss a dose of whatever medicine you're taking.

In many cases, drugs that have traditionally been prescribed four times a day have been found to work just as well when larger doses are taken twice a day, as in the case of strep throat medication.

Studies show that taking antibiotics such as penicillin or erythromycin two or three times a day instead of the usual four works just fine.

If taking medicines more than once or twice a day is hard to remember -- as it is for many people -- ask your doctor if there's an alternative drug that you could take less often. If there isn't, ask your doctor or pharmacist for practical tips on how to remember. Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington. Consultation is a health education column and is not a substitute for medical advice from your physician. Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.