Hi.
With your fasting that high (309), clearly you have
diabetes.
Now in the morning you took the medicine and checked your blood
sugar which has come quite under control. Note that machine readings can vary so much so that if u may have taken another reading from your glucometer at that very instance, the reading would've possibly been a little plus or minus from 152.
To add this, lab tests the blood sample from a vein, whereas glucometer measures from capillaries. So its an accepted difference, and has less effect on decision making for which anti-diabetic drug to use.
Regarding which is better of the two, it depends on ease or repeat samples rather than lab accuracy.
Evidently, rapid glucose samples are more easy and safer compared to multiple daily vein pricks for charting blood sugar.
Next Steps
For all practical purposes, continue keeping a Glucometer measures blood
sugar chart, and eventually once in 15-20 days u may get your Fasting and/or Random blood sugar measured at the Lab.