The answer depends on whether the question is about iron levels in human health or iron levels in Minecraft. For human health, the best iron level varies by age, gender, and health, but generally, optimal serum iron levels for adult males are about 50 to 150 mcg/dL and for adult females 35 to 145 mcg/dL. For ferritin, which indicates stored iron, the optimal range is often considered to be around 70-100 ng/mL for feeling well, although normal ranges start as low as 15 ng/mL. Hemoglobin levels reflecting iron status are about 13.8 to 17.2 g/dL for adult men and 12.1 to 15.1 g/dL for women.
For Minecraft iron ore mining, the best Y levels to find iron ore are Y=14 (most common underground level) and Y=232 (high-altitude mountain level). Iron ore does not spawn between Y levels 73 and 79. Other useful ranges include Y=-8 to -56 for large veins deep underground. These levels give the best chances of finding iron ore in the 1.20/1.21 Minecraft versions.
Please specify which "iron level" is being asked about—human iron levels or Minecraft iron ore mining levels—for a more tailored answer.
