Is take one twice a day good grammar?

Answer 1

'Take one twice a day' is acceptable, though it feels a little clumsy. 'Take one twice each day' is perhaps better English.

You could avoid the awkward feel of the phrase by adding a comma: 'Take one, twice a day' might do the trick.

Or, if in doubt, you can always rephrase or alter a word. In this case, you could say, 'Take one twice-daily', or 'Take one, twice daily'; both would be fine provided you use either the dash or the comma.

Rephrasing is frequently a good way to go and can save a great deal of time and thought, as can attention to the possibilities of punctuation.