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Pharmacy and Medications

With a Full Glass of Water?



I was recently on an antibiotic that the directions said to take "with a full 8 oz glass of water." I can`t drink that much water at once. Does that mean you are supposed to guzzle the whole glass of water at one time with the pill? Or is it okay to just take the pill with several swallows of water and then sip the rest of the water over the next hour or so? What happens if you don`t drink the whole glass of water with the pill? The antibiotic didn`t seem to work so they had to give me a different one, and I wonder if it didn`t work because I didn`t drink all the water I was supposed to with it?


Some medications do require drinking a full glass of water at the time they are taken to insure that the tablet does not get stuck in the throat during swallowing.

However, with antibiotics, the reason for the direction to “Take with a full 8 oz glass of water” is because it is important that patients be well hydrated while taking the medicine. If you take these medicines while dehydrated, unwanted and avoidable side effects can occur. For most of these drugs, this is because they are concentrated and removed from the body through the urine. Being well hydrated ensures that the drug will be able to be flushed from the system. For most of these medications, including the antibiotic you were most likely taking, it is not absolutely necessary to take a whole glass of water all at once, as long as you drink plenty of water throughout the day.


Antibiotics tend to work on specific types of infections. Generally, doctors pick an antibiotic they think will work based on their experience, the organ involved – lungs, bladder, etc., and the most likely bacterium involved. If the first choice does not work, they may choose a different antibiotic. This practice is common, and most  likely what happened in your case. Not drinking enough water should not have prevented the antibiotic from working.  If you are ever unsure about how much water you need to drink and at what time, you can always ask your pharmacist or your doctor for more information. Thank you for visiting NetWellness.

This response was prepared by Theresa Nolte, PharmD candidate at the University of Cincinnati College of Pharmacy.

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Response by:

Robert James Goetz, PharmD, DABAT
Assistant Professor of Pharmacy Practice
College of Medicine
University of Cincinnati