One symptom of gas that is not normally associated with it is the hiccup. Hiccups are harmless and will diminish on their own; they also help to release gas that is in the digestive tract before it moves down to the intestines and causes bloating. Important but uncommon causes of abdominal bloating include ascites and tumors. Causes
There are many causes of bloating, including: diet, irritable bowel syndrome, lactose intolerance, reflux, and constipation. Specific medical conditions like Crohns disease or bowel obstruction can also contribute to the amount of stomach bloating experienced. Common causes of abdominal bloating are:

Overeating
Gastric distension
Lactose intolerance, fructose intolerance and other food intolerances
Premenstrual syndrome
Food allergy
Aerophagia (air swallowing, a nervous habit)
Irritable bowel syndrome
Celiac disease
Non-celiac gluten sensitivity
Partial bowel obstruction
Gastric dumping syndrome or rapid gastric emptying
Gas-producing foods
Constipation
Visceral fat
Splenic-flexure syndrome
Menstruation, dysmenorrhea
Polycystic ovary syndrome and ovarian cysts
Alvarez syndrome, bloating of unknown or psychogenic origin without excess gas in the digestive tract
Massive infestation with intestinal parasites (e.g., Ascaris lumbricoides)
Diverticulosis
Certain medications, such as phentermine
Occurs in some due to salivary hypersecretion and dehydration.
The FDA is also collaborating with international regulators to share testing results for metformin.In July 2020, Lupin Pharmaceuticals pulled all lots (batches) of metformin after discovering unacceptably high levels of NDMA in tested samples.In August 2020, Bayshore Pharmaceuticals recalled two lots of tablets. Research
Metformin has been studied for its effects on multiple other conditions, including:

Non-alcoholic fatty liver disease
Premature puberty
Cancer
Cardiovascular disease in people with diabetes
AgingWhile metformin may reduce body weight in persons with fragile X syndrome,  whether it improves neurological or psychiatric symptoms is uncertain. Metformin has been studied in vivo (C. elegans and crickets) for effects on aging. A 2017 review found that people with diabetes who were taking metformin had lower all-cause mortality. They also had reduced cancer and cardiovascular disease compared with those on other therapies. References
Further reading
External links

"Metformin". Drug Information Portal. U.S. National Library of Medicine. "Metformin hydrochloride". Drug Information Portal. U.S. National Library of Medicine.