Question: how many milligrams of antihistamine can you take at one time?
Answer: Adults—1 to 2 milligrams (mg) every eight to twelve hours as needed. Children 12 years of age and older—0.5 mg to 1 mg two times a day as needed. Children 4 to 12 years of age—Use and dose must be determined by your doctor. Children and infants up to 4 years of age—Use is not recommended .