Serum is the clear, liquid portion of blood that remains after blood has clotted and blood cells are removed. Normally, serum has a pale yellow or straw-like color due to the presence of pigments like bilirubin and carotenoids. A distinctly yellow color in serum can indicate an unusual underlying condition.
What Yellow Serum Indicates
A noticeably yellow serum color usually points to elevated levels of bilirubin, a yellowish pigment. Bilirubin is a natural byproduct formed when old red blood cells break down.
Under normal circumstances, bilirubin travels to the liver, where it is processed and then excreted as part of bile, a digestive fluid. If there’s a disruption in this pathway, bilirubin can accumulate in the bloodstream, leading to hyperbilirubinemia, which manifests as yellow serum and often yellowing of the skin and eyes, known as jaundice.
Underlying Causes of Yellow Serum
Elevated bilirubin, and thus yellow serum, can stem from issues occurring at different stages of bilirubin processing within the body. These causes are generally categorized based on where the problem originates relative to the liver.
Conditions that cause excessive red blood cell breakdown, known as pre-hepatic causes, can lead to increased bilirubin production, overwhelming the liver’s ability to process it. Hemolytic anemia, where red blood cells are destroyed prematurely, is a common example. Another pre-hepatic cause is the reabsorption of large internal blood clots.
Problems within the liver itself are termed hepatic causes, where the liver’s capacity to process bilirubin is impaired. This can include liver diseases such as viral or alcohol-related hepatitis, and cirrhosis. Certain medications, like acetaminophen in overdose, or autoimmune conditions can also lead to impaired liver function and bilirubin buildup. A genetic condition called Gilbert’s syndrome also falls into this category.
Obstructions that prevent bilirubin excretion after it leaves the liver are known as post-hepatic causes. These typically involve blockages in the bile ducts that carry bile from the liver to the intestines. Common examples include gallstones, or inflammation and tumors in the gallbladder or pancreas.
When to Seek Medical Attention
If you notice your serum appears distinctly yellow, or if laboratory tests indicate elevated bilirubin levels, medical evaluation is advised. Yellowing of the skin or the whites of the eyes, known as jaundice, is a common sign that warrants a doctor’s visit. Jaundice typically becomes visible when bilirubin levels are two to three times the normal range.
Other symptoms that should prompt medical attention include dark, tea-colored urine, pale or clay-colored stools, unexplained itching, abdominal pain, or unusual fatigue. These symptoms can accompany elevated bilirubin and may signal liver dysfunction, bile duct obstruction, or blood disorders. A healthcare professional can accurately diagnose the underlying cause through further tests and recommend appropriate treatment.