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Your father is in imminent danger of Diabetic Ketoacidosis and its complications. And he HAS to get medical help. Although the chances are 20-30% it has to be taken care as it is a high risk condition.
The symptoms are not suggestive of a Flu. It could be bacterial infection (as in a wound , cellulitis, urinary tract infection etc). This infection could have precipitated high blood sugar which can result in a condition called Diabetic Keto acidosis. This could account for the symptoms of the bloated stomach and leg cramps.
He will need continuous monitoring of blood sugar, Insulin infusion (or shots). An antibiotic for the infection might be also needed. S. potassium values need to be monitored.
At home he should take libreal fluids (provided there is good urine output). Do continue the insulin. If you are experienced with Insulin dosage you can titrate it up for a couple of points if the sugar values are high.
Hope this helps
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