How many tablets of propranolol to take for a fast heart rate depends on how fast the heart rate is and how responsive the patient is to propranolol. When propranolol is used to treat arrhythmia, the starting dose is usually 10mg/dose, 3 times a day. When the heart rate is too fast, this dose may not achieve good control of the heart rate, and then the dose needs to be increased. Secondly, some patients are more sensitive to propranolol and can control their heart rate well with a smaller dose, while others are less sensitive and need a higher dose. In addition to the heart rate, the level of blood pressure also needs to be taken into account, as propranolol also has the effect of lowering blood pressure. If the blood pressure falls too low when the propranolol dose is increased, there is a risk of inadequate blood supply and the dose needs to be reduced appropriately. If the heart rate is well controlled and the blood pressure is still high, a combination of other antihypertensive drugs is required. Therefore, propranolol should always be used under the supervision of a specialist and the dose should be adjusted according to heart rate and blood pressure.