noun which may take the genitive case particle 'no'
in the blood; blood
Used attributively with の to mean 'in the blood' or 'blood-related', common in medical and scientific terms like 血中濃度 (blood concentration).
血中の酸素濃度を測定する。
Measure the oxygen concentration in the blood.
血中コレステロール値が高い。
Blood cholesterol levels are high.