Welcome at HCM
       I have gone through your query and being your doctor I completely understand your health concerns..
         The calcium potassium and 
magnesium levels need to be in normal range for the proper functioning of the human body..  
 Now coming towards the medicine you are taking.....furesimide and 
irbesartan are antihypertensive medications. They lower the blood pressure by increasing the urine output. In some instances the dose become relatively high causing low blood pressure along with 
electrolyte imbalance. You need to consult your doctor so that your medicines can be optimized to prevent these side effects...
    As far as 
warfarin is concerned the only related thing is PT INR ,your doctor will decide how much anticoagulantion is required for you. Normally INR is required  at value of 2 to 3..     
Amiodarone is concerned , it is antiarrhythmic drug and your doctor will adjust your dose..
   Last but not the least is 
insulin you should be cautious regarding 
hypoglycemia.. So use frequent small meals and  keep sweet candies in your pocket to prevent hypoglycemia... Your doctor will educate you about hypoglycemia and ways to prevent it.
    In short, you need to decrease your antihypertensive medications dose and also look carefully whether you are developing hypoglycemia or not.? 
    Do consult your doctor immediately..
  Hope your query is adequately addressed
        Regards
   Dr saad Sultan