Hello, The cramp like sensation over the fingers after using Methamphetamine is usually due to problem arising from poor blood circulation. This is called as vasovagal response, where Amphetamine s(meth) causes disturbance in regular functioning of the cardio-vascular system(usually seen in recreational drug abuse, rare at therapeutic dose). This leads to either rise or fall in blood pressure, numb or blue fingers, cardiac arrest and possibly death. The numbness of fingers need to be examined by a doctor to rule out permanent damage to circulation; which can cause damage blood vessels to nerves responsible for sensation in that area or even cause gangrene of the part. kindly consider seeing a doctor at the earliest to avoid permanent loss of function of the part affected. In addition, it is crucial to seek help for substance abuse/ addiction. Consider enrolling in couple anti-addiction support groups, community anti-addiction clinics and self help programs. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr. Ayesha Shareef