Other causes also include, diabetic people with a sudden increase in activity level as exercise is known to cause lower blood glucose. It can also be due to vomiting or diarrhea, having low-carbohydrate diets, an insulin-producing tumor (insulinoma), hormonal imbalances like low adrenal function and low growth hormone and also an accidental ingestion of antidiabetic drugs. Cancer can also cause low blood sugar in rare cases.