Fluorescent lamp (1) comprising a glass discharge vessel (2) in which a gas is present, which discharge vessel (2) is on two sides provided with a tubular end portion (3) having a longitudinal axis, which end portion (3) includes a glass stem (5), wherein an exhaust tube (6) extends axially outwardly from said stem (5) for supplying and/or discharging gases during the production of the lamp (1), wherein an electrode (8) extends axially inwardly through the stem (5) for generating and maintaining a discharge in the discharge vessel (2). The fluorescent lamp (1) is characterized in that it meets at least one of the following equations (I) or (II): or wherein R1/R2 = a degree for the effectivity for warming up the thin glass surface of the stem (5) where the exhaust tube (6) is connected to the stem (5) (the so-called 'weak spot') R3/R4 = a degree for the effectivity for transporting warmth through radiation from the stem (5) to the discharge vessel (2).