Diabetes when uncontrolled can cause weight loss, tiredness, weakness, lethargy, polyuria and polyphagia. So first of all I would make sure that his sugars are under control. Again there are many reasons for indigestion including long term diabetes causing diabetic gastropathy. So better to evaluate the causes before going to treatment it self. Liv 52 is a syrupy which is only used in few conditions again I wouldn’t recommend it before making sure what is the exact problem.
Next Steps
General investigation, get sugars under control