Prescribed drug use for bipolar disorder type I and II in clinical practice Practice guidelines based on available evidence and clinical consensus are available for the treatment of bipolar disorder. We surveyed to which extent those guidelines are implemented in clinical practice in Sweden. We analysed pharmacological treatment in patients with bipolar disorder in 2015 using the national quality register for bipolar disorder (BipoläR). We compared bipolar disorder type I (BDI) with type bipolar disorder type II (BDII). The vast majority of patients were prescribed a mood stabilizer either as monotherapy or as a part of combination therapy (BDI 87%, BDII 83%, p<0.001). Whereas lithium was the most common mood stabilizer in type I (BDI 65%, BDII 40%, p<0.001), lamotrigine was the most common mood stabilizer in type II (BDI 18%, BDII 42%, p<0.001). Antidepressants were less common in BDI than BDII (35% vs. 53%, p<0.001). Antipsychotic drugs (first or second generation) were more frequently used in BDI than BDII (49% vs 35%, p<0.001). Central stimulants were rarely used (BDI 3.1%, BDII 6.6%, p<0.001). Combining a mood stabilizer with an antipsychotic drug was more common in BDI than BDII (27% vs. 12%, p<0.001), whereas combining a mood stabilizer with an antidepressant was less common in BDI than BDII (16% vs 28%, p<0.001). We conclude that most patients are prescribed mood stabilizers and that the differences between BDI and BDII are rational given the differences in clinical manifestations. The use of antidepressants is surprisingly high given the long-standing debate about the risk and effectiveness of this class in bipolar disorder.