I was wondering if anyone has had a problem with a low heart rate while taking Lithium. I started out on 300mg and increased to 600mg after a week. I noticed that my heart rate when I increased it was in the 50s which is low for me but I wasn't too concerned. 3 weeks ago I increased to 900mg and last week I was feeling very fatigued and sluggish and noticed that my heart rate even up and walking around at work was 48. It has consistently been in the low 40s at night before bed so who knows what it drops to while I'm sleeping. Basically I feel okay other than being sluggish and having chest pain. I talked this over with my pdoc who says he doesn't think it's from the Lithium and he's not going to change the dose. It's the only thing that makes sense and my primary care doc agrees with me but I have yet to see a cardiologist to get his opinion. I already know that my heart is structurally fine so really the only thing that has changed has been the Lithium. My level came back fine 2 weeks agon so I'm not toxic. Just wondering if anyone has had any heart problems that came up after starting Lithium. Thanks for reading!