Final answer:
The patient is taking 40mg of LIS LASIX per day according to the prescription label, despite the initial instruction to take it twice daily. The dosage should be confirmed with a healthcare provider.
Step-by-step explanation:
The dosage of LIS LASIX that the patient is taking per day, according to the prescription provided, is 40mg. The question states that the patient has been advised to take the medication every morning and night, but then specifies that the prescription bottle indicates 40mg daily. The correct dosage following the prescription label would be 40mg per day, even though there seems to be a contradiction between the initial instruction and the label on the bottle. It's essential to clarify this with the healthcare provider, given that the patient is currently dehydrated and hypokalemic, as incorrect dosing may worsen these conditions.