What should be the blood sugar level for a normal person?
For a non-diabetic a ‘normal’ fasting blood glucose level should fall in the range 70 to 99 mg/dL (milligrams per deciLiter) (3.9 to 5.5 mmol/l (millimoles per litre) if you use the International Standard of blood glucose measurement), though several studies have revealed that fasting blood sugar (glucose) levels in the 90+ mg/dL (5+ mmol/l) indicates that that person MAY be in the very beginning stages of developing insulin resistance, a pre-cursor to the development of type 2 diabetes mellitus.
A two hour post prandial (after eating) reading for a non-diabetic would not normally rise above 140 mg/dL (7.8 mmol/l). I say normally as there are occasions when it could go higher, such as if the person being tested had an underlying infection at the time of testing; the person being tested as undergoing a period of extreme stress at the time of testing; or the person being tested was taking certain types of medication which are known to cause a rise in blood glucose levels. (These medications often include steroids, such as the types prescribed for the treatment of asthma, or for treating certain specific types of infection.)
A fasting blood glucose level of 126 mg/dL (5.5 mmol/l) on two or more separate occasions, when tested by a doctor, would be sufficient grounds for a doctor to diagnose diabetes. (I don’t know the laws in India, but in the West ONLY a practising medical doctor has the authority to diagnose diabetes.)
A random blood test of 200 mg/dL (11.1 mmol/l) would be sufficient for a doctor to diagnose diabetes, but you would, in all likelihood, find that the doctor would wish to carry out further testing to ensure that it isn’t something else that’s affecting blood glucose levels.