That equates to 14.7 sick days per person a year - half a day more than in 2012.
Health Insurer the Techniker Krankenkasse (TK), which carried out the research, blamed the rise on last year’s cold winter at the start of 2013.
Gudrun Ahlers from TK said: "Our data shows that the outbreak of colds weirdly tends to come in odd years. In 2013 each employee was off for an average of 2.4 days with respiratory problems. In 2012 it was only 1.9 days."
From 2012 to 2013 sick leave from colds increased by 24.3 percent.
It reached its climax on February 21st 2013 when the number of workers off ill was a record-breaking 5.81 percent, according to TK.
But for the first time in the history of TK's report, mental health disorders have not increased.
Psychologically-related sick leave including for depression and stress had an annual growth rate of five to eight percent in the past decade.
But with 2.5 days off per person in 2013, it was the same level as the year before.
The health insurer analyzed sick leave of 4.1 million employees insured by them for the study. The full report will be published in April.