Best, the nation's most-influential insurance ratings agency, maintained WellPoint's A grade, which means it is in excellent position to pay future medical claims.
But Best lowered its outlook on the Indianapolis-based health insurer from positive to stable.
Analysts praised WellPoint's large membership, diverse customer base and strong earnings.
But they ended their report by saying, "Organic membership growth appears to have slowed from recent economic conditions and increased competition. A.M. Best has concerns regarding the organization's growth potential, especially in the highly competitive commercial market, without acquisitions."