What If I Took Amoxicillin Once a Day Instead of Every 12 Hours?

Hi! I'm glad you asked a pharmacist about this instead of guessing!    

Three days of taking too little amoxicillin might result in you not getting the treatment you need.

Since the medication was prescribed to be taken every 12 hours, that is the way it should be taken and now the main question is whether your 7-day course needs a few extra days. That would be a decision for your prescriber.

Why Amoxicillin Is Dosed Every 12 Hours

Amoxicillin is a penicillin-type antibiotic, and your body eliminates it quickly.

After one dose, the amount in your blood drops over several hours, so by the second half of the day there's very little left to work against the bacteria. That's why it's prescribed either every 8 hours or every 12 hours, based on which strength you are taking.

Taking it once a day for three days means the infection received about half the intended medicine, with long periods where levels ran low. It's possible that may have slowed your treatment or possibly caused it to not work at all.

Spread out dosing also gives bacteria more opportunity to develop resistance, which is the main reason antibiotics are intended to be taken exactly as directed.

Resuming Twice-Daily Dosing Without Doubling Up

Don't take two doses at once to make up for those you missed. Extra amoxicillin in a single dose doesn't speed your recovery and mainly adds stomach upset and diarrhea. Take your next dose at the usual time, then another about 12 hours later, and continue that rhythm.

You'll also have more tablets/capsules remaining in the bottle than you typically would at this point. Some prescribers restart the 7-day count on the day correct dosing begins, while others simply add a few days to what you've already done.

The correct length also depends on what's being treated.

For strep throat, for example, guidelines differ between a shorter 5 to 7 day course and a full 10 days, depending on the goal of treatment, while sinus and chest infections have their own timelines. That's another reason the call is worth making instead of deciding on your own.

If you end up needing to restart your treatment, be sure to work with your doctor and pharmacy to get your prescription updated so you can fill the appropriate amount of the drug for a complete course.

Signs the Infection Isn't Responding

Most people begin feeling better within two or three days of correct dosing. Since you've effectively had a slow start, watch more closely than usual for how things are trending, and contact your doctor if you notice any of these.

• A fever that comes back or climbs after a couple of days back on the every-12-hour schedule.
• Shortness of breath, chest pain, or coughing up blood-streaked mucus.
• Feeling clearly worse rather than gradually better.
• Rash, hives, facial swelling, or difficulty breathing, which can signal a penicillin allergy. Stop the medicine and seek care right away if this happens.
• Watery or bloody diarrhea with cramping or fever, during treatment or even weeks later, since antibiotics can trigger a serious gut infection.

Final Words

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