Humana's chief financial officer Susan Diamond will step down in January, the insurer announced Tuesday. | Susan Diamond will exit the CFO role after three years and a total of eighteen across different positions at Humana,

Humana's Susan Diamond is stepping down as CFO and handing over the role to a top finance executive at a BlackRock-owned fund, in a major shakeup in the health insurer's management ranks following the appointment of a new CEO earlier this year.

The replacement for the CFO role at Humana serves in the same role at Global Infrastructure Partners and Fannie Mae.

Humana Inc said on Tuesday that Chief Financial Officer Susan Diamond was stepping down and Celeste Mellet would replace her, effective Jan. 11. The CFO change comes as the health insurer struggles to manage its medical costs related to its large business of Medicare Advantage insurance plans,