The usual vomit from the stomach is pale brown and sour. When your vomit contains the bile and other intestinal contents, it will be bright yellow to dark green and bitter.
Certain foods or spices, such as green leafy vegetables, fruit juices, carrots, curry or turmeric, and medicinal syrups can also color the vomit yellow or green.
Vomiting Green or Yellow Bile
1. Vomiting on an empty stomach, in the morning
When you are vomiting on an empty stomach, the bile from the upper part of the small intestine is usually the only thing that can come up.
- Hangover after excessive alcohol drinking 
- Morning sickness in pregnant women 
- Food poisoning, intolerance or allergy 
- Migraine headache
- Medications (aspirin, antidepressants, antibiotics, morphine), iron supplements or chemotherapy 
Severe conditions :
- Pancreatitis or pancreatic cancer
- Kidney failure
- Adrenal insufficiency
- Labyrinthitis or other disorders of the inner ear
- Diabetic ketoacidosis
- Cyclic vomiting syndrome (mainly in children) 
- Brain tumor or bleeding, or brain swelling due to water intoxication
- Poisoning with pesticides, carbon monoxide or other toxins
2. Bile reflux
Bile reflux refers to frequent backflow of the bile from the intestine into the stomach, where it mixes with food and can trigger vomiting. Causes of bile reflux are listed below.
Stomach conditions :
- An ulcer or cancer in the lower part of the stomach
- Partial stomach removal
- Gastric bypass surgery for weight loss
3. Intestinal obstruction (ileus) [1,5]
Increased pressure due to an intestinal obstruction can push the bile into the stomach. Common causes include:
- Severe constipation – fecal impaction
- Crohn’s disease
- Recent surgery
- Adhesions after abdominal surgery
- In infants:
- Congenital abnormalities
- Intestinal loops twisting (volvulus)
- In elderly:
NOTE: A newborn vomiting yellow or green contents should be checked by a doctor for an intestinal obstruction as soon as possible.
Vomiting Blood and Brown or Black Bile
The vomit can appear brown or black after consuming dark colored foods or beverages, such as chocolate, coffee or red wine, or after taking iron supplements or bismuth subsalicylate.
Some women report vomiting brown bile as part of morning sickness. This should not be a a cause of concern.
NOTE: Vomiting brown bile can result from intestinal obstruction (see above) or a bleeding stomach ulcer or cancer. The blood in the bile can also appear black, like coffee grounds.
Vomiting Blue Bile
Green vomit may appear blue-green under certain lights . The green bile in the vomit can turn blue when reacting with detergents in the toilet or sink.
Vomiting bile that is already blue when it comes out of your mouth can occur after the ingestion of blue colored beverages, candies or medications.
NOTE: Vomiting blue bile can also result from poisoning with copper sulfate  or antiseptics or pesticides that contain boric acid.
How to Stop Vomiting Bile
To reduce the risk of vomiting bile:
- Keep yourself well hydrated.
- Drink some plain water in the morning.
- Have frequent small meals.
- Avoid smoking [6,7].
- Avoid excessive alcohol drinking.
What to Eat After Vomiting Bile
Foods to avoid after vomiting bile:
- Alcohol, caffeinated and fizzy drinks and fruit juices
- Fatty foods: meat, oil, milk, cheese, eggs, chocolate
- Salty foods: canned foods, salty snacks, sauces, bagged soups
- Foods that cause bloating: legumes, oats, barley
- Spicy foods
You can try bland foods, such as:
- Whole grain bread
- Brown rice
- Green leafy vegetables
When To Visit a Doctor
When you are vomiting bile, and you can not think of an obvious cause, such as alcohol drinking or a migraine headache, visit a doctor, especially if you are experiencing:
- Vomiting brown or black bile
- Black stools
- Severe or prolonged abdominal pain, diarrhea, headache, dizziness or fatigue
A doctor may suggest investigations, such as blood tests or upper endoscopy, to find a cause of vomiting bile.
Treatment depends on the underlying condition:
- Bile reflux can be treated with medications, such as baclofen , cisapride , domperidone  or ursodeoxycholic acid ; bile salt sequestrants, such as cholestyramine, are less effective .
- Intestinal obstruction often requires urgent surgical treatment.
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- Phelps K et al, 2011, General Practice: The Integrative Approach, p.406
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