I Have Been Taking Metformin For 6 Months...started With One

i have been taking metformin for 6 months...started with one pill a day...then my doctor had me add a second pill about 3 months ago...at that time i started with itching that has gotten worse & wakes me up at night....since this started at the time i added the second pill, i am going off the pill till my next doctor visit in 6 weeks (which i cleared with him) is itching a know side effect for metformin? & how long till the medication TOTALLY leaves my body?