High cholesterol, when do you have to start taking medication (at what level)?

Depends on risk. Physicians generally decide to treat patients based on the LDL level. Individual risk factors help a provider determine what this number should be, it is not the same for everyone. For example, someone who has diabetes or has had a heart attach has a goal of <70 for their ldl, but usually are started on meds if it is over 100. Your doctor can calculate your specific goal.
Risk factors. There is no single trigger level for stating medication and it is driven more by LDL levels than total cholesterol. For people at very high risk the target level for LDL cholesterol is 70 mg/dl. For a person at low risk for heart disease medication may be initiated if the LDL level is higher than 130.