4 identical tablets

That you are given 4 identical tablets. Of which 2 are for cold and 2 for headache. 100mg each. All the tablets look the same. You have a patient and you have to provide him with the medicine. You must give him one tablet for cold and one for headache. But you do not know which one is for cold and which one for the headache. So how will you give it to him. If he has more than 100mg of a specific medicine he'll die.





Idea 1: 
Randomly select 2 tablets, break them into 4 pieces(make each tablet 2 identical pieces)  then give 2 pieces to the patient. Again do the same procedure. 


Idea 2 : 
Mix all the tablets in water and give the patient half of that solution.:)