While it is normal for blood pressure to fluctuate for all people (due to activity), any actual reading (or Heart Habit estimate) above 180 systolic or 110 diastolic may require emergency treatment.
If confirmed, call 911 immediately. Time is of the essence and through simple medication seldom requiring hospital stay, the blood pressure can be brought into a non-critical range quickly to then treat for longer term health.
While the blood pressure is one indicator, never ignore certain critical symptoms if you have hypertension - especially if measuring your blood pressure at the moment is not possible.
Most importantly, to prevent your blood pressure from ever reaching these critical levels, measure your blood pressure regularly and record for early warning signs that can be simple to address.