It's quite safe. Keep regular check on blood sugar. If bld sugar changes frequently then there are chances of hypoglycemia which can be dangerous.

Thnxs for Question. its gastation diabetes so will be ok after delivery. but before delivery you should control your suger level with diet modification, for that you should consult dietician. and regarding metformine i think u should regularly check your sugar level with test call ORAL GTT. that will give you true idea abt control over sugar. it should be less than 140 mg. and  consult your gynecologist regualry .

Hiii Common side effects are Abdominal or stomach discomfort,cough or hoarseness,decreased appetite,diarrhea,fast or shallow breathing,fever or chills,general feeling of discomfort,lower back or side pain,muscle pain or cramping,painful or difficult urination,sleepiness....less commonly seen effects are Anxiety,blurred vision,chest discomfort,cold sweats,coma,confusion,cool, pale skin,depression,difficult or labored breathing,dizziness,fast irregular, pounding, or racing heartbeat or pulse,feeling of warmth,headache,increased hunger,increased sweating,nausea,nervousness,nightmares,redness of the face, neck, arms, and occasionally upper chest,seizures,shakiness,shortness of breath,slurred speech,tightness in the chest,unusual tiredness or weakness,wheezing, RareBehavior..... change similar to being drunk difficulty with concentrating,drowsiness,lack or loss of strength,restless ,... As such there are no reported effect s on pregnancy... Should be careful while lactation