Hoping you can tell me, is high heart rate dangerous?

Heart rate: Chronic high heart rate can cause cardiomyopathy.

Sorry but more: Specifics are required. Not necessarily as we get get high heart rates with strenuous exercise for example.

How high?: High heart rate more than 100 beats per minute can be a sign of lack of physical conditioning, endocrine disease like hyperthyroidism, sign/symptom of heart disease, dehydration, lung disease like asthma/copd, drug induced like to much caffeine/ energy drinks, chronic disease like liver and renal insufficiency, etc. You need a history and physical to evaluate the reason.