Diarrhea, defined as an increase in the frequency or looseness of bowel movements, is a common condition that usually resolves on its own within a few days. However, there are certain situations in which it is important to visit a doctor for diarrhea. These include:

1. Persistent diarrhea lasting more than a few days.
2. Severe abdominal pain or cramping.
3. Blood or mucus in the stool.
4. High fever or signs of dehydration, such as dark urine, dry mouth, or dizziness.
5. Significant weight loss or malnutrition.
6. Symptoms that are accompanied by other symptoms such as vomiting, nausea, or a rash.
7. If you are taking medication such as blood thinners, or have any underlying medical conditions, such as HIV/AIDS, cancer, or inflammatory bowel disease.

If you are experiencing any of these symptoms, it is important to visit a doctor for an evaluation. They will be able to determine the cause of your diarrhea and recommend an appropriate course of treatment.

Diarrhea is a common condition that can be caused by a variety of factors. Some of the main causes of diarrhea include:

1. Gastrointestinal infections: The most common cause of diarrhea is an infection caused by a virus, bacteria, or parasite. These types of infections can be contracted through contaminated food or water, or by person-to-person contact.
2. Medications: Certain medications can cause diarrhea as a side effect, such as antibiotics, blood pressure medications, and laxatives.
3. Food intolerances or allergies: Lactose intolerance and gluten intolerance can cause diarrhea. Also, some people may have an allergic reaction to certain foods.
4. Inflammatory Bowel Disease (IBD): Crohn's disease and ulcerative colitis are chronic conditions that cause inflammation in the gastrointestinal tract, leading to diarrhea.
5. Gastrointestinal disorders: Certain gastrointestinal disorders such as irritable bowel syndrome (IBS) and functional diarrhea can cause chronic diarrhea.
6. Hormonal disorders: Some hormonal disorders, such as hyperthyroidism, can cause diarrhea.
7. Malabsorption: In some cases, diarrhea can be caused by malabsorption, which is when the body is unable to absorb certain nutrients from food properly.

It's important to know that diarrhea can have different causes, and sometimes the cause is not clear. A healthcare professional will be able to evaluate your symptoms and recommend an appropriate course of treatment.

A Gastroenterologist is best for Diarrhea. You'll likely first seek medical care for Diarrhea from your family doctor or general practitioner. You may be referred to a specialist in the digestive system (gastroenterologist) if your doctor suspects a more advanced case of Diarrhea.