if memory serves i believe 15 or less is the top end for plasma zinc, locally at least.
into the abyss:
- The impact of plasma zinc status on the severity of prostate cancer disease (2019)
The PCa patients had markedly reduced plasma zinc status compared to controls (cases: 9.42±3.02 µmol/L versus controls: 15.23±4.47 µmol/L; p<0.001). Low zinc status was more pronounced within the severe grade and advanced PCa disease subgroups (p<0.001).
- A previous study reported in 2014 from South-eastern Nigeria had also observed similarly reduced plasma zinc in men with prostate cancer compared to apparently healthy controls (cases: 22.5±6.4 µmol/L versus controls: 25.9±9.1 µmol/L; p<0.05) ...
- Białkowska et al.  had recently reported a higher zinc status among Polish PCa patients compared to controls. While Eken et al.  found no difference in zinc status of Turkish PCa patients compared to controls. These reports [8,9] are at variance to our finding and could be related to environmental, dietary, genetic or study methodological differences.