UnitedHealth Group says its fourth-quarter net income slipped 1 percent, as growing medical costs countered revenue gains for the nation's largest health insurer.

The Minnetonka, Minn., insurer says it earned $1.24 billion, or $1.20 per share, in the three months that ended Dec. 31. That compares with $1.26 billion, or $1.17 per share, in the last quarter of 2011. Total revenue climbed 11 percent to $28.77 billion, but medical costs grew 12 percent to $20.8 billion.

Analysts forecast earnings of $1.20 per share on $28.23 billion in revenue.

The company says it still expects 2013 earnings to range between $5.25 and $5.50 per share. Analysts forecast $5.56 per share.

UnitedHealth is the first insurer to report earnings every quarter. Many see it as a bellwether for other insurers.