Why do people with diabetes have a hard time keeping a balance blood-glucose level?

They don't synthesize any glucagon hormone, to
help shuttle extra glucose out of the cell when
there is too much

they don't synthesize any hormones to keep their
blood pressure in check

they don't synthesize any hormones to keep their
blood pH in check
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they don't synthesize any insulin hormone, to
help shuttle glucose into the cell when there is a
need