Is methamphetamine harmful for diabetic person? what's the possible effect?

It is harmful to ALL: People, let alone diabetics. Stimulants, especially those related to adrenaline (like amphetamine and methamphetamine) increase blood sugar and other stress hormones, and clamp down blood vessels which can already be damaged in diabetics. Methamphetamine prematurely ages people, can cause heart attack and stroke, depression, anxiety and paranoia to the point of psychosis. Don't start it!