-You can use Qiagen or any company miRNA Isolation kit which includes Blood sample also, follow the manufacturer instruction's and go ahead.
-Or you can isolate total RNA from blood using Qiagen RNA isolation kit or Takara RNAIso plus. Then convert all the miRNA from total that RNA using mIRCurry miRNA cDNA kit. you can use that cDNA directly for real time PCR using SYBr.