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You have developed numbness
after injecting meth. It might be due to injury to vein which resulted due to injection. It finally resulted in inflammation or thrombophlebitis
of vein. As infection is spreading whole hand is developing numbness and discoloration. But as you have mentioned that you have also developed numbness on opposite hand also, but thrombophlebitis is usually localized.
Other possibility is allergic reaction
due to some adulteration in meth. Due to this you might have developed numbness in both extremities. I advise you to visit ER as soon as possible because to contain spread medicines are necessary.
Dr. Seikhoo Bishnoi