Yes, levels of 590 is super high. I am surprised that you are not very ill with it.
I would suggest that you take another reading. But before you do, wash your hands thoroughly to make sure that they are clean and that there is no contamination of sugar on your fingers in the event that you picked up anything sugary.
Your glucose monitor only shows the amount of glucose in your blood at the time you take your reading.
If you haven't seen your doctor yet, do make an urgent appointment so that you can be given the right advice and information and medication to bring down the levels and know how to manage and control your sugar levels once they reach the required goal. Your doctor will advise you on this.
In the meantime, you can help yourself, by eating a healthy and well balanced diet and cut out (or drastically cut down) on sugary and processed foods. Eating brown bread for example is a better option that having white bread. Cutting out cakes, biscuits and being aware of the sugar content of low fat foods. Although low fat foods may be low in fat, they can contain a lot of sugar.
with blood sugar of 590, please go directly back to the emergency room.
A blood sugar of 590 is a medical emergency. You need to be given insulin. You may well be Type 1, not type 2 and are at risk of diabetic coma / ketoacidosis.
I am very surprised that you were even discharged from hospital with blood sugars so out of control.
Do not eat any foods with carbs in them and drink plain water.
Please let us know if you are ok, and that you got treated.
As Jemma said wash and re test. If your BG is still that high (over 500 ) Sally is correct you need to be taken the ER do not drive you could pass out and crash. Do not eat ANY carbohydrate it will only raise your BG. drink only water.