Metformin lowers blood sugar levels, if you blood sugar levels are otherwise normal, and you are taking medication that lowers it further, you may be experiencing symptoms of Hypoglycemia (low blood sugar). Symptoms can include:
Feeling shaky.
Being nervous or anxious.
Sweating, chills and clamminess.
Irritability or impatience.
Confusion.
Fast heartbeat.
Feeling lightheaded or dizzy.
Hunger.