A patient admitted to the hospital for stomach inflammation received strong antibiotics that unexpectedly caused a serious blood-clotting problem. Doctors discovered the antibiotics had killed helpful bacteria in his gut that normally help the body make vitamin K, a nutrient essential for blood clotting. His blood became dangerously thin, which could have caused life-threatening bleeding during surgery. A simple vitamin K injection fixed the problem. This case shows that doctors need to watch patients taking strong antibiotics for signs of bleeding problems, especially those who aren’t eating normally.

The Quick Take

  • What they studied: How a patient developed a dangerous blood-clotting disorder after receiving antibiotics for a stomach infection
  • Who participated: One adult male patient admitted to the hospital with severe abdominal pain from inflammation of the colon
  • Key finding: Strong antibiotics killed the good bacteria in the patient’s gut that help produce vitamin K, leading to severe blood-clotting problems that developed within days of starting treatment
  • What it means for you: If you’re taking strong antibiotics for a serious infection, especially while eating very little, ask your doctor about monitoring your blood clotting. This is rare but serious, and early detection can prevent dangerous bleeding during surgery

The Research Details

This is a case report, which means doctors documented what happened to one specific patient in detail. The patient came to the hospital with severe belly pain and was diagnosed with acute diverticulitis (inflammation of the colon). He was started on intravenous antibiotics and told to eat very little. When doctors prepared him for surgery, they ran blood tests to make sure his blood could clot properly. The initial tests looked normal, but when they repeated the tests before surgery, they found something shocking: his blood had lost the ability to clot normally. The doctors ran additional specialized tests to figure out what caused this sudden change and discovered that specific clotting factors that depend on vitamin K had disappeared from his blood.

Case reports are important because they alert doctors to rare but serious side effects they might not expect. This case is valuable because it shows how a combination of factors—strong antibiotics, limited food intake, and the body’s natural gut bacteria being killed—can create a dangerous medical emergency. Understanding this connection helps doctors watch for warning signs in other patients facing similar situations.

This is a single case report, which means we can’t say this happens to everyone taking antibiotics. However, the doctors did thorough testing to confirm their diagnosis, and the patient’s quick recovery after vitamin K treatment strongly supports their explanation. The main limitation is that this describes one person’s experience, not a pattern across many patients. Doctors should use this information to be alert, but more research would be needed to understand how often this actually happens.

What the Results Show

The patient’s blood tests changed dramatically between his hospital admission and his pre-surgery evaluation. When he first arrived, all clotting tests were normal. However, within a few days of receiving broad-spectrum antibiotics and eating very little, his blood-clotting ability had severely declined. Specialized tests showed that the patient was missing vitamin K-dependent clotting factors—proteins that the body needs to make blood clot. The doctors ruled out other causes like blood-thinning medications or inhibitors that might block clotting. When they gave the patient intravenous vitamin K, his blood-clotting ability returned to normal, confirming the diagnosis. This rapid development of a serious clotting problem could have caused life-threatening bleeding during the planned surgery if doctors hadn’t caught it during routine pre-surgery testing.

The case highlights that vitamin K deficiency from antibiotic use is a recognized but often overlooked complication. The patient’s situation was particularly risky because he was both taking strong antibiotics that killed his gut bacteria and eating very little, creating a double problem for vitamin K production. The doctors noted that while vitamin K deficiency from antibiotics is known in medical literature, it’s not always watched for carefully enough, especially in patients who aren’t eating normally.

Medical literature has documented that broad-spectrum antibiotics can cause vitamin K deficiency, but this case is notable because the problem developed so quickly and severely. Most documented cases develop more gradually. This patient’s rapid decline suggests that the combination of antibiotic use plus dietary insufficiency creates a particularly dangerous situation. The case reinforces existing medical knowledge but emphasizes that doctors should be more vigilant about screening patients at risk.

This is a report of a single patient, so we cannot say how common this problem is or whether it would happen the same way in other people. We don’t know if certain antibiotics are more likely to cause this than others, or if some patients are more at risk. The case doesn’t tell us how many patients taking similar antibiotics develop this problem or whether early vitamin K supplementation could prevent it. More research studying many patients would be needed to answer these questions.

The Bottom Line

Doctors should consider checking blood-clotting ability in patients taking strong antibiotics, especially those who are eating very little or have limited food intake. Patients taking antibiotics should mention to their doctor if they’re not eating normally. If a patient needs surgery while on antibiotics, pre-surgery blood tests are essential. Vitamin K supplementation may be considered for high-risk patients, though this would need to be discussed with a doctor. Confidence level: Moderate—based on this case and existing medical knowledge, but more research is needed.

Hospital patients receiving strong antibiotics for serious infections should be aware of this risk, especially if they’re eating very little. Surgeons and doctors preparing patients for surgery should be alert to this possibility. People with digestive problems that limit food intake may be at higher risk. This is less relevant for people taking antibiotics at home for minor infections while eating normally. Pregnant women and people taking blood-thinning medications should definitely discuss this with their doctors.

In this case, the clotting problem developed within days of starting antibiotics. Vitamin K injections worked quickly to restore normal clotting. However, the timeline can vary depending on how much vitamin K the body has stored and how long the antibiotics are used. If you’re concerned, talk to your doctor about when to expect improvement.

Want to Apply This Research?

  • If you’re taking strong antibiotics while hospitalized or eating very little, track any signs of unusual bleeding: nosebleeds, bleeding gums, bruising easily, or blood in urine or stool. Note the dates you start antibiotics and any changes in your diet or appetite.
  • If you’re on antibiotics and eating very little, try to eat vitamin K-rich foods when possible (leafy greens, broccoli, Brussels sprouts) or ask your doctor about vitamin K supplementation. Keep a simple log of what you eat and any bleeding symptoms to share with your doctor.
  • For patients on long-term antibiotics: weekly check-ins with your doctor about bleeding symptoms, monthly blood tests if recommended, and immediate reporting of any unusual bruising or bleeding. After antibiotics end, continue monitoring for 1-2 weeks as your gut bacteria recover.

This case report describes one patient’s experience and should not be used for self-diagnosis. Vitamin K deficiency from antibiotics is rare but serious. If you’re taking antibiotics and experience unusual bleeding, bruising, or nosebleeds, contact your doctor immediately. Do not stop taking prescribed antibiotics without medical advice. Always discuss concerns about antibiotic side effects with your healthcare provider. This information is educational and not a substitute for professional medical advice.