Male 26, low rbc 4.39*10^12, total haemoglobin 13.2g/dl, mcv 88fl, mch 30pg, mchc 34 g/dl, reti index 0.84%, esr 2ml/hr cause of low rbc?

Borderline anemia: Your hemoglobin is also a wee bit low for a man (most men have 13.5 or more). The explanation might be something as simple as having drunk a few extra glasses of water before the blood draw so that you could also provide a urine sample. Your physician may want to check you now for occult blood loss, repeat the cbc, or begin an anemia workup now despite normal indices. Good luck.