Key Takeaways Jefferies downgraded Humana, warning how the latest Medicare ratings will affect results.The analysts noted that data from federal regulators showed Humana had a huge dropoff in Medicare customers.

The insurer’s stock sank to its lowest level in more than a decade after the federal government lowered the rating for one of its most popular plans.

Humana’s stock was headed for another sharp selloff on Tuesday, toward a more than four-year low, after the government cut its rating on one of the health insurer’s large Medicare Advantage plans because it missed some performance measures.