HGH 10 iu Only Came Up with 5.8 ng/ml

so I been on hgh for 6 months 5 iu a day split and i decided to do the hgh blood test where you inject 10iu and then get your blood work in 3 hrs. From what i been reading it should be at least 20 and and mine was 5.8 I did it subq though and not into the muscle, does that make a difference ?