[OMFG!You'reActuallySmart!]

If you're being tested, it may be as simple as an ordinary blood and urine test (urine test could suggest diabetes indirectly but blood test is what you want). They'd measure for different things though, such as A1C level, current blood sugar, ketone presence (want none of them otherwise you're in a real mess) and many others. They'd also ask you about things such as vision changes (increase blood sugar alters visual acuity), thirst and urination, possibly do a throat swab if needed, sugary-like smell and metallic/blood taste in mouth when no blood is there, etc... .

My aunt has diabetes and for the insulin pump, she does not care for it but others like it so look into it and decide.

If you need to administer yourself insulin, it's done in the belly area for a few reasons but the simplest is that it's easiest to access with minimal discomfort. If you know basic neuroanatomy and functional neuroanatomy, think somatosensory homunculus and this will make sense. If this is gibberish to you, then ignore it.

There are 2 systems of measuring, I think one is mmol/L and I'm not sure what the other one is, I think it has dL or something. Anyways, you can convert one to the other and certain meters use one over the other, as do the doctors, so when you test your blood, you'll be given a numerical reading and through trial-and-error, you figure out the base dose for insulin. Depending on your food amount, hunger, carbs/sugars and reading, you adjust the insulin amount accordingly. There are different types of insulin and meds to amplify the effects if need be.