A 70-year-old woman came to the hospital with severe stomach pain and dangerously high acid levels in her blood. Doctors initially thought she had a serious infection, but testing showed something different. The real problem was a combination of two common medications she was taking—metformin for diabetes and linezolid for a bone infection—plus missing important vitamins. When doctors stopped these medications and gave her vitamin supplements, she recovered quickly. This case shows that doctors need to look at all the medicines patients take, not just assume a serious infection is causing the problem.

The Quick Take

  • What they studied: Why a patient developed dangerously high acid levels in her blood and what caused it
  • Who participated: One 70-year-old overweight woman who came to the emergency room with stomach pain
  • Key finding: Two common medications (metformin and linezolid) combined with vitamin deficiencies caused the dangerous acid buildup, not an infection as doctors first suspected
  • What it means for you: If you take metformin or linezolid and develop unusual symptoms, tell your doctor about all your medications. Make sure you’re getting enough vitamins, especially B1 and vitamin C. This doesn’t mean these drugs are bad—just that doctors need to monitor patients carefully and consider all possible causes of symptoms.

The Research Details

This is a case report, which means doctors documented what happened with one specific patient to share what they learned. The patient came to the emergency room with severe abdominal pain. Doctors ran blood tests and imaging scans to figure out what was wrong. They discovered her blood had very high levels of lactate, which is a chemical that builds up when the body isn’t getting enough oxygen or when certain things go wrong with metabolism. At first, doctors thought she might have a serious infection in her bile ducts (biliary sepsis), but the test results didn’t match that diagnosis.

The doctors looked carefully at all the medications the patient was taking at home. She was on linezolid, an antibiotic used to treat a bone infection (osteomyelitis), and metformin, a common diabetes medication. They also discovered she wasn’t eating well and was missing important vitamins, particularly vitamin C and B1 (thiamine). The doctors decided to stop the two medications and give her fluids, electrolytes, and vitamin supplements to see what would happen.

Within 36 hours of stopping the medications and starting supplements, her lactate levels returned to normal and she started feeling much better. This dramatic improvement suggested that the combination of the two medications, plus the vitamin deficiencies, was the real cause of her dangerous acid buildup.

Case reports like this are important because they help doctors recognize patterns they might otherwise miss. While this is just one patient’s story, it teaches an important lesson: when patients have multiple medications and health conditions, doctors need to think carefully about how everything might be connected. This case shows that serious-sounding symptoms don’t always have the obvious cause doctors expect.

This is a single case report, which is the lowest level of scientific evidence. It describes what happened to one person, not a large group. However, case reports are valuable for alerting doctors to unexpected side effects or drug interactions. The findings are based on careful observation and clear cause-and-effect (the patient got better when the medications were stopped). Readers should know this doesn’t prove these medications always cause this problem—it just shows it can happen in certain situations.

What the Results Show

The patient’s blood lactate level was dangerously elevated when she arrived at the hospital. Doctors initially suspected a serious infection because high lactate often signals that tissues aren’t getting enough oxygen. However, imaging and blood tests ruled out the expected infection. The key discovery was that she was taking two medications known to potentially cause lactate buildup: metformin (for diabetes) and linezolid (for bone infection). Additionally, blood tests showed she was deficient in vitamin C and B1, both important for how the body processes energy.

When doctors stopped both medications and started giving her intravenous fluids, electrolytes, and vitamin supplements, her lactate level normalized within 36 hours. This rapid improvement was remarkable and suggested that the combination of medications plus vitamin deficiencies was causing the problem, not an infection. The patient continued to recover well after this treatment change, indicating that the diagnosis and treatment were correct.

The case also highlighted the importance of nutritional status in patients taking these medications. The patient was malnourished, which made her more vulnerable to problems from her medications. Her recovery depended not just on stopping the medications but also on replacing the missing vitamins and electrolytes. This suggests that patients on long-term medications should have their nutritional status checked regularly.

It’s already known that both metformin and linezolid can cause lactate buildup in certain situations, especially in patients with kidney problems or other risk factors. However, this case is notable because it shows how the combination of two medications plus vitamin deficiencies created a perfect storm. Most previous reports focused on one medication or one clear cause. This case demonstrates that doctors need to consider multiple factors working together.

This is a single case report, so we can’t know how often this combination of problems occurs or who is most at risk. The patient had multiple health issues and was taking multiple medications, so it’s hard to know exactly which factor was most important. We don’t know if other patients with similar medication combinations and vitamin deficiencies would have the same outcome. Doctors can’t use one patient’s story to make treatment decisions for everyone, but it does provide valuable warning signs to watch for.

The Bottom Line

If you take metformin or linezolid, this case suggests several reasonable precautions: (1) Make sure your doctor knows about all medications you’re taking, (2) Eat a balanced diet with adequate vitamins, especially B vitamins and vitamin C, (3) Have your kidney function checked regularly if you take metformin, and (4) Tell your doctor immediately if you develop unusual symptoms like severe fatigue, difficulty breathing, or persistent nausea. Confidence level: Moderate—this is based on one case, but the warning signs are worth taking seriously.

This case is most relevant to people taking metformin for diabetes or linezolid for infections, especially those who are older, overweight, or not eating well. It’s also important for doctors and pharmacists to consider when patients on these medications develop unexplained symptoms. People with kidney problems should be especially careful with metformin. However, this doesn’t mean these are bad medications—millions of people take them safely. It just means careful monitoring is important.

In this case, improvement happened very quickly—within 36 hours of stopping the medications and starting supplements. However, this was an emergency situation with severe symptoms. For people taking these medications without problems, there’s no need to make sudden changes. If you have concerns, discuss them with your doctor at your next appointment.

Want to Apply This Research?

  • If you take metformin or linezolid, track your energy levels and any unusual symptoms (fatigue, shortness of breath, nausea, muscle weakness) daily using a simple 1-10 scale. Note any days when you feel unusually tired or unwell, and share this pattern with your doctor.
  • Set a daily reminder to eat foods rich in B vitamins (whole grains, eggs, nuts, leafy greens) and vitamin C (citrus fruits, berries, bell peppers). Log these foods in your nutrition tracker to ensure adequate intake, especially if you’re on long-term medications.
  • Create a monthly check-in reminder to assess overall wellness. Track weight, energy levels, appetite, and any new symptoms. If you notice a pattern of declining energy or new symptoms appearing, flag this for discussion with your healthcare provider at your next visit.

This case report describes one patient’s experience and should not be used to make decisions about your own medications. Metformin and linezolid are safe and effective when used appropriately. Do not stop taking these medications without talking to your doctor first. If you experience unusual symptoms while taking these medications, contact your healthcare provider immediately. This information is educational and not a substitute for professional medical advice, diagnosis, or treatment.