Hemoglobinuria: Unexpected Signals You Must Not Ignore

Urine color changes are easy to blame on dehydration, foods, or supplements, but some color shifts reflect what is happening in the blood rather than the bladder. Hemoglobinuria refers to hemoglobin in the urine, typically after red blood cells rupture within the circulation (intravascular hemolysis). It is different from hematuria (intact red blood cells in urine) and can be a meaningful clue to conditions that may also affect the kidneys, oxygen delivery, and overall health.

This article is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalized guidance and treatment.

What is Hemoglobinuria?

Hemoglobinuria occurs when free hemoglobin passes through the kidneys and appears in urine, often turning it reddish-brown or cola-colored. A common clinical clue is a urine dipstick that reads positive for “blood,” but microscopic examination shows few or no red blood cells—suggesting pigment (hemoglobin or sometimes myoglobin) rather than bleeding into the urinary tract. Because hemoglobin itself can be irritating to kidney tubules, significant or prolonged episodes may contribute to acute kidney injury, especially if accompanied by dehydration or other stresses.

It’s also important to distinguish hemoglobinuria from myoglobinuria, which can occur after muscle breakdown (rhabdomyolysis). Both can darken urine and produce a positive dipstick for “blood,” so laboratory context and follow-up testing are key.

What are the Common Causes of Hemoglobinuria?

Most causes relate to intravascular hemolysis—red blood cells breaking apart within blood vessels. Potential triggers include immune-mediated hemolysis (for example, autoimmune hemolytic anemia), transfusion reactions, certain infections (such as malaria in appropriate travel or exposure settings), severe burns, and mechanical destruction from devices or abnormal blood flow (rarely, issues involving prosthetic heart valves). Some people experience “march hemoglobinuria,” a form of exertion-related hemolysis historically associated with repetitive foot-strike or intense endurance activity.

A notable, rarer cause is paroxysmal nocturnal hemoglobinuria (PNH), an acquired stem cell disorder that makes blood cells vulnerable to complement-mediated destruction. PNH can present with episodic dark urine and is also associated with fatigue and elevated clotting risk. Because the cause determines urgency and treatment, hemoglobinuria should be approached as a sign that needs explanation, not a diagnosis by itself.

What Symptoms Indicate the Presence of Hemoglobinuria?

The most visible signal is dark urine—often described as tea-, cola-, or red-brown colored—especially when it appears suddenly or recurs. However, urine appearance alone is not definitive; some people have pigment in the urine without dramatic color change. Symptoms linked to hemolysis may include unusual fatigue, shortness of breath on exertion, dizziness, headaches, or paleness from anemia. Jaundice (yellowing of the skin or eyes) can occur when hemolysis increases bilirubin production.

Some scenarios require urgent evaluation, particularly if hemoglobinuria is accompanied by fever, chills, back pain, chest pain, fainting, marked weakness, new swelling, reduced urine output, or severe abdominal pain. If symptoms occur soon after a blood transfusion, it should be treated as an emergency, as transfusion reactions can escalate quickly.

How is Hemoglobinuria Diagnosed?

Clinicians typically start with urinalysis. A dipstick that is positive for “blood” with few or no red blood cells on microscopy raises suspicion for hemoglobinuria (or myoglobinuria). Additional urine testing may look for protein, casts, and other markers of kidney stress.

Blood tests help confirm hemolysis and assess severity. Common evaluations include a complete blood count (to check anemia), reticulocyte count (bone marrow response), lactate dehydrogenase (often elevated in hemolysis), haptoglobin (often low), and bilirubin levels. Kidney function is checked with creatinine and electrolytes, and sometimes additional markers if acute kidney injury is suspected. Depending on context, further testing may include a direct antiglobulin (Coombs) test for immune causes, infectious workups, and, when PNH is a concern, flow cytometry assessing proteins such as CD55 and CD59 on blood cells.

What Treatment Options are Available for Hemoglobinuria?

Treatment focuses on the underlying cause and on protecting the kidneys during episodes. For mild, transient cases linked to exertion or dehydration, medical guidance may emphasize hydration, rest, and monitoring, while still ruling out more serious contributors if episodes recur. When hemolysis is immune-mediated, clinicians may use therapies such as corticosteroids or other immunosuppressive approaches, tailored to the specific diagnosis and patient factors.

If hemoglobinuria is associated with infection, treatment targets the infectious cause and supports organ function. In severe hemolysis or anemia, transfusion may be needed, and any suspected transfusion reaction is managed urgently with immediate cessation of the transfusion and supportive care.

For PNH, disease-directed therapies may include complement inhibitors that reduce intravascular hemolysis and its complications. In the United States, FDA-approved options for PNH include eculizumab, ravulizumab, and pegcetacoplan, prescribed and monitored by specialists with attention to vaccination and infection risk mitigation. Additional management can include anticoagulation in selected cases, folate supplementation if indicated, and careful kidney monitoring. Because treatment choice depends on symptoms, lab findings, clotting risk, and overall health, individualized specialist care is central.

Hemoglobinuria is a meaningful clinical signal—sometimes benign and short-lived, but sometimes a marker of significant hemolysis that warrants prompt evaluation. Understanding how it differs from hematuria, noticing associated symptoms, and using targeted testing can clarify the cause and guide appropriate treatment while reducing the risk of kidney injury and other complications.