Certain medications need to be taken with plenty of water. Depending on the medication, there are different reasons for this:

  • The medication could cause you to become dehydrated (e.g., lithium)
  • The medication could damage the kidneys or lead to kidney stones if too much of it reached the kidney at the same time (e.g., cotrimoxazole, indinavir). Water helps to “dilute” the extra medication so that too much medication does not go through the kidneys at once.

In general, all medications should be taken with a full glass of water, unless your doctor or pharmacist recommends otherwise. If your medication needs to be taken with “plenty of water”, you may need to drink more than a full glass of water with your medication. This varies with the medication, but can be as much as 1.5 L every day, as is recommended for indinavir.

It is also important to drink enough water throughout the day to avoid dehydration. People’s needs will vary, but most people need 6 to 8 glasses a day, and even more if it is hot, or when they are physically active.