Background: Thyroid hormones act on nearly every cell in the body including red blood cells. Thyroid hormones are also important to proper development and differentiation of all cells of the human body. Human Immunodeficiency Virus (HIV) is a virus that destroys certain cells in the immune system. The aim of this study was to determine free triiodothyronine (FT3), free thyroxine (T4) and red cell indices level of HIV subjects attending clinic at Enugu State University of Science and Technology Teaching Hospital. Study Design: Case control study. Place and Duration of Study: Human Immunodeficiency Virus (HIV)  clinic and Haematology Laboratory both of Enugu State University of Science and Technology Teaching Hospital, between August and October 2021. Methodology: Sixty HIV subjects and thirty apparently healthy individuals within the age range of 30 - 60 years were recruited for this study. Free triiodothyronine (FT3), free thyroxine (FT4), hemoglobin (HGB), packed cell volume (PCV), red blood cell count (RBC), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), red cell distribution width standard deviation (RDW-SD), red cell distribution width coefficient of variation (RDW-CV) were determined in HIV subjects and apparently healthy individuals.  Results: There was significant difference in MCV (125.79+/- 7.57 vs 78.89+/- 5.71 fl), MCH (23.17+/- 2.10 vs27.21+/- 3.68 pg), MCHC (25.08+/- 2.74 vs30.09+/- 3.27 g/dl), RDW-SD (61.52+/- 7.55 vs46.23+/- 5.87 fl), RDW-CV (23.06+/- 5.78 vs43.87+/- 1.28 fl) and PCV (39.38+/- 3.06 vs31.75+/- 2.44 %) between patients on antiretroviral therapy (ART) and ART-naïve patients respectively. There was significant difference in T4 (8.29+/- 1.29 vs 6.12 µg/dl), MCV (78.89+/- 5.71 vs 84.47 +/- 3.79 fl), MCH (27.21+/- 3.68   vs 29.20 +/- 2.27 pg), RDW-CV (43.87+/- 1.28 vs 12.51 +/- 1.08 fl) and PCV (31.75+/-2.44vs 37.63+/-2.95 %) on ART-naïve patients and apparently healthy subjects respectively. There was a positive correlation between FT3 and MCH in HIV patients on antiretroviral therapy (ART) (p= 0.016). Conclusion: In people taking antiretroviral therapy, mean cell haemoglobin, mean cell hemoglobin concentration and red cell distribution width coefficient of variation significantly reduced, as well as raised mean cell volume and red cell distribution width standard deviation. This study also observed reduced mean cell haemoglobin, mean cell haemoglobin concentration and mean cell volume in ART- naïve subjects.