The main risk factor for stroke is high blood pressure.[6] Other risk factors include high blood cholesterol, tobacco smoking, obesity, diabetes mellitus, a previous TIA, end-stage kidney disease, and atrial fibrillation.[2][6][7] An ischemic stroke is typically caused by blockage of a blood vessel, though there are also less common causes.[12][13][14] A hemorrhagic stroke is caused by either bleeding directly into the brain or into the space between the brain's membranes.[12][15] Bleeding may occur due to a ruptured brain aneurysm.[12] Diagnosis is typically based on a physical exam and supported by medical imaging such as a CT scan or MRI scan.[8] A CT scan can rule out bleeding, but may not necessarily rule out ischemia, which early on typically does not show up on a CT scan.[9] Other tests such as an electrocardiogram (ECG) and blood tests are done to determine risk factors and rule out other possible causes.[8] Low blood sugar may cause similar symptoms.[8]