what is normal glucose level in our body ? is 5.1 is slightly to diapers?

Normal glucose level in human body is 65 - 110

65-120 is normal blood glucose range. as for the diaper thing, l have no idea what you mean.

the normal fasting blood glucose range is 3.5-6.0 mmol/L.

Above 7 is classed as probable diabetes and 6.1-6.9 is impaired fasting glucose.

With the Oral Glucose Tolerance Test, less than 7.8 mmol/L is normal

mahes !
The following information summarizes the meaning of the test results.

From 70 to 99 mg/dL (3.9 to 5.5 mmol/L) Normal fasting glucose

From 100 to 125 mg/dL (5.6 to 6.9 mmol/L) Impaired fasting glucose (pre-diabetes)

126 mg/dL (7.0 mmol/L) and above on more than one testing occasion Diabetes

For more on diabetes
http://hypogglycemiainfo.blogspot.com
http://diabetesindetail.com