Abstract: The invention proposes a liquid heating bag 1, in particular, a blood heating bag and a bag heating means 30 for heating liquids, e.g. cooled blood, which flow through the liquid heating bag 1, to a temperature suitable for transfusion. The liquid heating bag 1 has a flow volume 3 formed by at least two flexible plastic foils which are connected to each other at four delimiting edges 5, 6, 7, 8, wherein the flow volume 3 has a flat, substantially trapezoidal basic shape which is delimited by the delimiting edges 5, 6, 7, 8. An inlet line opening 12 and an outlet line opening 14 are disposed on a first delimiting edge 5, and an insertion tab 15 is disposed on a second delimiting edge 6 opposite to the first delimiting edge 5. The liquid heating bag 1 has a liquid flow guiding seam 20 which is formed by connecting the plastic foils in the region of the flow volume 3. The insertion tab 15 is formed as part of the plastic foils, which projects past the second delimiting edge 6.