Hi welcome to HCM
I have gone thru your query regarding elevated BSL , It is a matter of concern and is  very common problem these days . Do you know why ? Because  of  our faulty food habits and derailed life style and obesity is outcome and so is 
diabetes , hyper tension and other diseases  . 
You have not mentioned your age and how old is your problem ?What alll you are   taking in your diet ? You have told you are not taking  'extra sugar ' means still you are taking sugar ? with so high BSl ?
 You must keep in mind not to include  sugar or sugary products , carbs in your diet . 
Constipation is mother of all ills . so be careful .
Our health depends  on 'what  we eat ,when we eat and how we eat .  and our activity level .
 Treatment with tablets and 
insulin is not enough anyway .A strict diet control and regular exercise to control weight is a part of the therapy. 
I suggest you to take balanced regular diet .Include all essential nutrients less carbs , more of fiber,protein , vitamins ,minerals in natural form as  fruit ,green leafy veges , supplements full of antioxidants - lemon juice ,bitter gourd juice 25 ml , 
Aloe vera juice +Amla juice , coconut water , turmeric powder  with a cup of hot milk + a T spoon almond oil, almonds ,walnut , a few to count , and proper , exercise regular walk yoga ,pranayam - deep breathing will fulfill your requirement of balanced diet ,and overall 
detoxification of your system .
Last but not the least shun your mental 
stress , worry ,anger to get sound sleep practice 
meditation to enhance resistance from diseases and pave way for healthy , happy ,disease free life if above regimen followed regularly . 
Hope this helps you solve your query . Take care .All the best
Don't hesitate to come back for further query if any .