Direct bilirubin (also called conjugated bilirubin) is the “processed” form of bilirubin your liver has made water-soluble so it can be excreted in bile. A direct bilirubin blood test helps evaluate bile flow and liver handling of bilirubin, especially when bilirubin is elevated. Mild increases (such as 0.4–0.6 mg/dL) are often interpreted alongside total bilirubin, ALT/AST, alkaline phosphatase (ALP), GGT, and symptoms to determine whether the pattern suggests cholestasis (reduced bile flow), liver inflammation, or temporary/benign variation.

The Indirect Bilirubin test measures how much bilirubin is in your blood. It originates from the breakdown of hemoglobin in the red blood cells, but must be removed by your liver. 

Total bilirubin measures the amount of bilirubin — a yellow-orange pigment produced when old red blood cells are broken down — circulating in the blood. The liver captures bilirubin, processes it, and excretes it through bile into the intestines. When this process is disrupted by liver disease, bile duct obstruction, or excess red blood cell breakdown, bilirubin accumulates in the blood and may cause jaundice (yellowing of the skin and eyes), dark urine, and pale stools. The normal total bilirubin range in adults is 0.2–1.2 mg/dL; mild elevation (up to 2–3 mg/dL) is common and often benign. Total bilirubin is interpreted alongside direct and indirect bilirubin fractions, ALT, AST, ALP, and GGT to identify the likely cause and organ involved.

Bilirubin is primarily derived from metabolism of hemoglobin. Only conjugated bilirubin is excreted into the urine and normally only trace amounts can be detected in urine.

Bilophila wadsworthia is a sulfate-reducing bacterium that naturally occurs in the human gut microbiome, typically in small quantities. This anaerobic, gram-negative bacillus was first isolated in 1989 and is known for its ability to thrive in bile-rich environments. While B. wadsworthia is present in 50-60% of healthy individuals, an overgrowth of this species has been associated with various health concerns. It produces hydrogen sulfide, which in excess can contribute to gut inflammation and has been linked to conditions such as inflammatory bowel disease, irritable bowel syndrome, and colorectal cancer. B. wadsworthia's growth is particularly stimulated by diets high in saturated fats and taurine-rich foods like meat and dairy products. In controlled studies, this bacterium has been shown to exacerbate metabolic dysfunctions in mice fed a high-fat diet, leading to increased inflammation, intestinal barrier dysfunction, and glucose dysregulation. The presence and abundance of B. wadsworthia in a BiomeFX report may provide insights into potential gut dysbiosis and associated health risks, especially in the context of dietary habits and metabolic health.

Bilophila Wadsworthia is a gram negative, anaerobic, sulfidogenic bacterium resistant to β-lactam antibiotics. This pathobiont is commonly found in patients with appendicitis and it has been associated to the Western diet (high in fats and animal proteins), as well as severe malnutrition. A recent study in animals showed that a high fat diet stimulates the growth of B. Wadsworthia, which causes inflammation, dysfunction in the intestinal barrier and bile acid metabolism, hepatic steatosis and dysfunctional glucose metabolism. Interestingly, the co-administration of a probiotic strain (Lactobacillus rhamnoses) reduces the generated inflammation and limits the metabolic impairment.

Biotin is required for proper metabolism of fats and carbohydrates. Biotin-dependent enzymes catalyze the addition of carboxyl groups (COO-) from bicarbonate, for use in fatty acid biosynthesis, gluconeogenesis, lipogenesis, propionate metabolism, and leucine catabolism.

Biotin, also known as Vitamin B7, is a water-soluble B-complex vitamin that plays a critical role in various metabolic processes and is commonly included in blood panel tests to assess nutritional status. It acts as a coenzyme for carboxylase enzymes, pivotal in the synthesis of fatty acids, amino acids, and the generation of glucose from non-carbohydrate sources. Biotin is essential for the proper functioning of the nervous system and plays a role in maintaining skin, hair, and mucous membrane health.

Bismuth is found in alloys, catalysts, cosmetics, paints, magnets, ceramics, pharmaceuticals, x-ray contrast media,
and semiconductors. Bismuth is generally non-toxic, although very high levels may cause nausea, vomiting, and diarrhea.
Renal, neurological, and hematological problems have been associated with bismuth toxicity. Hair is not a sensitive
specimen for bismuth toxicity; blood and urine are most commonly used.

Used in alloys, electronics, batteries, crystal ware, cosmetics, flame retardants,and in antimicrobial therapy (H. pylori), antiseptic dressings, paraffin paste. Bismuth medical therapies exhibit high therapeutic effects and little side effects, though over-dosage can cause toxicity.

Very limited absorption in the GI tract. When absorbed, it binds mainly to transferrin and lactoferrin, interacts with enzymes due to a high affinity to cysteine residues, blocking the active site. Can accumulate in the kidney, lung, spleen, liver, brain, and muscles, while being eliminated in urine and feces via bile and intestinal secretions.

Bismuth is found in alloys, catalysts, cosmetics, paints, magnets, ceramics, pharmaceuticals, x-ray contrast media,
and semiconductors. Bismuth is generally non-toxic, although very high levels may cause nausea, vomiting, and diarrhea.
Renal, neurological, and hematological problems have been associated with bismuth toxicity. Hair is not a sensitive
specimen for bismuth toxicity; blood and urine are most commonly used.

Fecal bismuth (Bi) provides an estimate of a recent oral exposure to the element. Bi is a non-essential element of relatively low toxicity. Absorption is dependent upon solubility of the Bi compound, with insoluble Bi excreted in the feces while soluble forms are excreted primarily in the urine. Sources of Bi include: cosmetics (lipstick), Bi containing medications such as ranitidine Bi-citrate, antacids (Pepto-
Bismol), pigments used in colored glass and ceramics, dental cement, and dry cell battery electrodes.

Several organometallic Bi compounds are used for bactericidal and fungicidal applications.

Symptoms of moderate Bi toxicity include constipation or bowel irregularity, foul breath, blue/black gum line, and malaise. Unusually high levels of Bi retention in the body may result in nephrotoxicity (nephrosis, proteinurea) and neurotoxicity (tremor, memory loss, monoclonic jerks, dysarthria, dementia). Urine elements analysis may be used to corroborate Bi absorption for a period of days or a few weeks after
the exposure.

Bismuth is a heavy, brittle metal with a white, silver-pink hue, typically found in small amounts in the earth's crust and often used in various industrial, cosmetic, and pharmaceutical applications, such as in the manufacturing of low-melting alloys, cosmetics, and some medications, particularly those used for gastrointestinal issues. In the context of a hair test, the presence of bismuth can indicate exposure to these products or environmental sources. While trace amounts of bismuth are generally considered non-toxic to humans, elevated levels can be a cause for concern.

Used in alloys, electronics, batteries, crystal ware, cosmetics, flame retardants,and in antimicrobial therapy (H. pylori), antiseptic dressings, paraffin paste. Bismuth medical therapies exhibit high therapeutic effects and little side effects, though over-dosage can cause toxicity.

Very limited absorption in the GI tract. When absorbed, it binds mainly to transferrin and lactoferrin, interacts with enzymes due to a high affinity to cysteine residues, blocking the active site. Can accumulate in the kidney, lung, spleen, liver, brain, and muscles, while being eliminated in urine and feces via bile and intestinal secretions.