What causes lower back pain and black stool? Related conditions and treatments

Lower back pain and black stool causes are not usually connected. Lower back pain is very common and can be caused by poor posture, heavy lifting, osteoarthritis, menstrual cramps, and more. Black stool can be caused by certain medications, foods, or supplements, but it can also be a sign that you’re bleeding from inside your gastrointestinal (GI) tract.

Most of the time, the causes of lower back pain and black stool are not the same, so experiencing both symptoms could be coincidental. However, there are a few conditions that can cause both symptoms: diverticulitis in the large intestine, gastrointestinal cancer, and frequent or heavy use of over-the-counter NSAIDs.

Key takeaways:

• Lower back pain and black stool are both common symptoms that are not usually connected. Dark stool may be caused by foods, supplements, medications, or bleeding in the upper digestive tract. Lower back pain may be caused by muscle strain, injury, digestive problems, infections, or inflammation.
• Typically, lower back pain and black stool do not require treatment unless they do not stop on their own. They typically resolve without treatment within a few days, but black, tarry stool may require medical treatment.
• Save on prescriptions for lower back pain with a SingleCare prescription discount card.

What causes lower back pain and black stool?

“Because the causes of black tarry stools are indicative of upper gastrointestinal bleeding, they will not tend to cause low back pain,” says David Bilstrom, MD, owner of Autoimmune Functional Medicine and director of the International Autoimmune Institute & Bingham Memorial Center for Functional Medicine in Blackfoot, Idaho. He adds that lower GI problems can cause lower back pain, but the blood in stool from lower GI problems would be bright red rather than black.

There are only a few situations in which black stool and lower back pain may be linked, according to Harish Gagneja, MD, gastroenterologist and chief medical officer at Austin Gastro in Texas:

• Diverticulitis in the large intestine
• Gastrointestinal cancer
• Frequent or heavy use of over-the-counter NSAIDs to treat lower back pain, which can lead to an ulcer that causes black stool

Sometimes, having black stool is harmless and short-lived. Causes of black stool, with or without unrelated back pain, include: 

• Eating dark-colored foods, such as blood sausage, beets, black licorice, or blueberries
• Taking iron supplements
• Using medications that contain bismuth subsalicylate, such as Pepto-Bismol or Kaopectate

In other cases, black stools are caused by bleeding in the upper GI tract: the esophagus, stomach, or upper small intestine. Red blood turns black and sticky when processed through the small intestine, large intestine, and rectum. The blackened, tarry stool is called melena.

GI problems that may cause melena include:

• Peptic ulcer (bleeding ulcer in the stomach or small intestine)
• Internal bleeding from an injury, trauma, a tear in the gastrointestinal lining, or swallowing a foreign object
• Severe inflammation (esophagitis or gastritis)
• Enlarged veins that bleed in the esophagus or stomach (often due to liver cirrhosis)
• Inflammatory bowel disease (IBD): Ulcerative colitis or Crohn’s disease
• Severe cases of irritable bowel syndrome (IBS)
• Cancer

Ultimately, if you have lower back pain and black stool at the same time, there is a good chance that your symptoms are not related to the same underlying condition. If you see a doctor about either issue, you should still discuss both symptoms in case of a connection.

Should I be worried about lower back pain and black stool?

The mere presence of lower back pain and black stool is not a medical emergency. Back pain has many causes and often goes away on its own. Black or dark-colored stool with a standard shape and texture (not sticky or “tarry”) might not be cause for concern. However, sticky, black stool with no apparent dietary reason can indicate internal bleeding. In that case, call your doctor right away.

“Anyone having black stools, unless they are taking Pepto-Bismol or iron supplements, should seek medical attention regardless of the presence of back pain,” Dr. Gagneja says. “Gastrointestinal bleeding can be dangerous and life-threatening if not diagnosed and treated in a timely manner.”

Upper digestive tract bleeding does not typically cause lower back pain in addition to black stool, but there usually are other symptoms. Go to the emergency room if you have black poop along with the following:

• Abdominal cramping
• Nausea
• Dizziness
• Trouble swallowing
• Shortness of breath
• Blood in vomit

“This type of bleeding is a medical emergency requiring immediate attention,” Dr. Bilstrom warns. This is especially true for people with a history of stomach ulcers, gastrointestinal conditions, or liver problems. These populations have an increased risk of GI bleeding and should take black stool seriously, even without other symptoms.

How is the cause of lower back pain and black stool diagnosed?

A healthcare provider can diagnose any medical conditions causing lower back pain and black stool. The process starts with an overview of your medical history and a physical examination. Be prepared to answer a variety of questions, including:

• When did you begin experiencing lower back pain and black stool?
• How many times has your poop been black? Are your bowel movements black every time?
• What are your eating habits? Have you consumed blueberries, black licorice, lead, or Pepto Bismol?
• What medications and supplements do you take?
• Do you have a history of bowel problems, such as IBS and IBD, or a serious medical condition, such as liver disease, pancreatic cancer, or colorectal cancer?
• Are you experiencing other symptoms, such as bloody stool, abdominal pain, diarrhea, constipation, nausea, or unintended weight loss?

“Your medical provider will likely order a stool test for blood and blood tests to check for anemia,” Dr. Gagneja says. Depending on the suspected cause of your symptoms, other tests might include a CT scan of your abdomen, an endoscopy, and, in some cases, biopsies of lesions or other abnormalities found in the GI tract. A CT scan is noninvasive imaging of the inside of your body. In an endoscopy, a specialist passes a flexible tube with a camera into your esophagus, stomach, and duodenum (upper small intestine) to check for tears, ulcers, lesions, or broken blood vessels. If these tests don’t reveal a clear cause of your symptoms, you might also need to make an appointment for a colonoscopy or X-ray.

How to stop lower back pain and black stool

How to get rid of lower back pain and black stool depends on the cause. Even some causes of bleeding, like peptic ulcers or gastritis, can go away on their own, but that’s not always the case.

Lower back pain and black stool treatments might include avoiding NSAIDs if you have a peptic ulcer linked to medication use or controlling stomach acid with proton pump inhibitors (PPIs) or H2 blockers if you have bleeding from esophagitis. If your doctor is concerned about advanced cancer or heavy internal bleeding that could lead to shock, you will likely need immediate treatment, such as surgery.

Remember, it’s important to see a healthcare provider to determine how to treat lower back pain and black stool. These symptoms may be linked, or they may have entirely different underlying causes. The best treatment plan is one that tackles the root of the problem.

The role of spinal health in digestive function

While the thoracic spine (vertebrae T1-T12) is connected to the chest and stomach, the lumbar spine (L1-L5) is connected to most of the digestive system—the intestines and colon. While Dr. Gagneja says bowel and spinal problems are not commonly associated, he explains that spinal issues affecting the nerves controlling bowel function can lead to constipation or bowel incontinence. In other words, spine problems can cause bowel problems.

Cauda equina syndrome (CES) is a prime example of spinal problems affecting nearby organs. CES occurs when there is severe nerve compression at the end of the spinal cord, known as the cauda equina. Symptoms of CES can include lower back pain and inability to control urination or defecation, but CES is unlikely to cause black stool. There is a lack of evidence that chiropractic adjustments can help treat gastrointestinal disease, but spinal adjustments may help with bowel problems that stem from compressed nerves.

Ultimately, spinal health plays a significant role in overall health and pain-free living. The nerves rooted in the spine can cause pain in the abdomen, pelvis, and beyond. Regular spinal checks can help prevent more severe pain issues in the future.

Living with lower back pain and black stool

Lower back pain is very common in the general population. People with stomach ulcers or IBD are more likely to experience upper GI bleeding, so black stools and back pain can happen regularly. 

If you are living with IBD or experiencing recurrent stomach ulcers, a few lifestyle changes can help with symptom relief while you continue following your prescribed treatment plan:

• Stretch and exercise regularly to destress and promote spinal health.
• Avoid foods that are difficult to digest, such as spicy foods, fried foods, and fatty foods.
• Avoid NSAIDs like aspirin and ibuprofen.
• Take glutamine supplements, which can help heal the gut lining.
• Quit smoking.
• Focus on stress management.

Related: 6 surprising ways stress can affect your body

Most importantly, tell your doctor if you’re experiencing lower back pain and black stool

Lower back pain and black stool causes may include lifestyle factors, such as taking NSAIDs or iron supplements. The causes of lower back pain and black stool may resolve on their own without treatment. However, if lower back pain and black stool continue, worsen, or are accompanied by vomiting, nausea, fever, or bloody stool, it could be a sign of internal bleeding and require immediate medical attention. A healthcare provider can rule out infections or other serious health conditions. Visit your doctor to determine the best treatment for lower back pain and black stool.