Explore our database of over 4000 laboratory markers.

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Fecal Zonulin

Gut Zoomer by Vibrant Wellness, Vibrant Wellness

Optimal range:   25.1 - 160.8 ng/mL

Fecal zonulin is a biomarker of intestinal permeability, often referred to as “leaky gut.” Zonulin is a protein that regulates the tight junctions between intestinal cells. When zonulin levels rise, these junctions loosen, allowing larger molecules — such as food proteins, toxins, or microbes — to pass into the bloodstream, which can trigger inflammation and immune responses.

Measuring zonulin in stool is considered more gut-specific than serum testing, since blood levels can also be influenced by production in other organs like the liver, heart, and brain. Elevated fecal zonulin has been associated with conditions such as celiac disease, non-celiac gluten sensitivity, Crohn’s disease, ulcerative colitis, IBS-D, metabolic syndrome, obesity, type 1 diabetes, and autoimmune disorders. Lifestyle factors like smoking, stress, and processed food intake can also affect zonulin release.

Fecal zonulin is most informative when used alongside other stool markers (such as calprotectin, secretory IgA, or anti-gliadin IgA) to help assess gut barrier integrity and distinguish between inflammatory bowel disease and other gastrointestinal disorders.

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Ferritin

Blood Health

Optimal range:   30 - 400 µg/dL , 5.37 - 71.6 µmol/L , 30 - 400 ng/mL , 30 - 400 ug/L

Ferritin is a protein that serves as a storehouse for iron in the body. When iron supplies dwindle, ferritin releases some into the blood. Therefore, a blood ferritin test is an indication of how much iron is stored in the body. Iron is used primarily by red blood cells to carry oxygen to other cells, and as such Ferritin is vital to blood health. 

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Ferritin

NutriStat, NutriPATH

Optimal range:   30 - 400 ug/L

Protein that stores iron. Red blood cells need iron to carry oxygen around the body such as the liver, bone marrow, and muscles. An indirect marker of the total amount of iron stored in the body; hence, serum ferritin is used as a diagnostic test for iron- deficiency anemia.

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Ferritin (female range)

Blood Health

Optimal range:   15 - 150 ng/mL , 15 - 150 ug/L

Ferritin is a protein that serves as a storehouse for iron in the body.

When iron supplies dwindle, ferritin releases some into the blood. Therefore, a blood ferritin test is an indication of how much iron is stored in the body. Iron is used primarily by red blood cells to carry oxygen to other cells, and as such Ferritin is vital to blood health. 

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Ferritina

Brazilian Biomarkers

Optimal range:   30 - 400 ug/dL

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FGF-23

Bone Health

Optimal range:   44 - 215 RU/mL

What is FGF-23?

FGF-23, or fibroblast growth factor 23, is a hormone-like protein that plays a critical role in phosphate and vitamin D metabolism. It is primarily produced by bone cells (osteocytes and osteoblasts) and acts mainly on the kidneys to regulate:

  • Phosphate excretion in urine

  • Vitamin D activation

  • Calcium-phosphate balance

FGF-23 is part of a feedback system that helps maintain normal blood phosphate levels. When phosphate levels rise, FGF-23 secretion increases to help eliminate excess phosphate through the urine and reduce vitamin D activation.

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FIB 4 Index

Liver Health

Optimal range:   0 - 1.3 Units

The FIB-4 Index, a non-invasive and widely used clinical tool, is instrumental in the assessment of liver fibrosis, particularly in patients with chronic liver diseases such as Hepatitis C and Non-Alcoholic Fatty Liver Disease (NAFLD). This index, calculated using a simple formula that incorporates age, platelet count, and liver enzyme tests (AST and ALT levels), offers a cost-effective and easily accessible means of evaluating liver health.

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FIB-4 Index

Liver Health

Optimal range:   0 - 1.29 index

If your FIB-4 Index result shows an Indeterminate risk for advanced liver fibrosis, it means that your score falls within a range where the risk of significant liver scarring (fibrosis) is uncertain. This does not confirm or rule out advanced liver fibrosis but suggests that further testing may be needed for a more definitive assessment.

Understanding FIB-4 Index

The FIB-4 Index is a non-invasive biomarker used to estimate liver fibrosis risk. It is calculated using age, AST (aspartate aminotransferase), ALT (alanine aminotransferase), and platelet count. The score is typically interpreted with the following cutoffs:

  • Low Risk: FIB-4 < 1.3 (unlikely to have advanced fibrosis)
  • Indeterminate Risk: FIB-4 between 1.3 and 2.67 (uncertain risk)
  • High Risk: FIB-4 > 2.67 (higher likelihood of advanced fibrosis)

What an Indeterminate Result Means

  • Your FIB-4 score is neither clearly low nor high, meaning that advanced liver fibrosis cannot be ruled out.
  • This result may be due to age, mild liver enzyme abnormalities, or borderline platelet counts.
  • It does not necessarily mean you have liver disease, but further evaluation is recommended.

Next Steps

If your FIB-4 result falls in the indeterminate range, your healthcare provider may:

  • Order additional tests, such as the FibroScan (elastography), liver biopsy, or more advanced fibrosis markers (e.g., ELF test, APRI score).
  • Monitor your liver health over time with repeat FIB-4 testing and blood work.
  • Evaluate potential causes of liver injury, including fatty liver disease (NAFLD/NASH), viral hepatitis, alcohol use, metabolic conditions, or medication effects.

Key Takeaway

An indeterminate FIB-4 result means further evaluation is needed to clarify your liver fibrosis status. It does not confirm serious liver disease but suggests that monitoring and possibly additional testing are advisable.

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Fibrillarin

Systemic Sclerosis

Optimal range:   0 - 11 SI

U3-RNP antibodies target the U3 small nucleolar ribonucleoprotein (U3-RNP) complex, which consists of the protein fibrillarin and U3 RNA. These antibodies are found in about 4% to 10% of patients with SSc, and are especially common in African American SSc patients (approximately 30%). U3-RNP antibodies are rarely found in patients with other autoimmune disorders; thus, the presence of these antibodies supports a SSc diagnosis. 

These antibodies occur most often in dcSSc, but they can also occur in lcSSc.

U3-RNP antibodies are associated with multiorgan involvement, including the heart, kidneys, muscle, lungs, and gastrointestinal system. Their presence is an independent risk factor for the development of PAH, and PAH is the most common cause of death in U3-RNP–positive patients. Therefore, their presence indicates a poorer prognosis.

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FIBRINOGEN

NutriStat, NutriPATH

Optimal range:   2 - 4.5 g/L

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Fibrinogen

Lipid Panel

Optimal range:   0 - 370 mg/dL , 0 - 3.7 g/L

Fibrinogen is a key marker included in the Inflammation and Oxidation Test panel by Boston Heart Diagnostics, primarily due to its critical role in the body's clotting process and its association with inflammation. Essentially, fibrinogen is a blood plasma protein that's converted into fibrin by the action of the enzyme thrombin during blood clot formation. This process is crucial for stopping bleeding and initiating the healing process following an injury. However, elevated levels of fibrinogen can indicate an increased risk of clot formation within the blood vessels, which is a significant concern because it can lead to blockages, thereby increasing the risk of heart attacks and strokes.

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Fibrinogen Activity

Blood Health

Optimal range:   193 - 507 mg/dL , 1.93 - 5.07 g/L

It’s used to determine the level of fibrinogen in your blood. Fibrinogen, or factor I, is a blood plasma protein that’s made in the liver. Fibrinogen is one of 13 coagulation factors responsible for normal blood clotting.

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Fibrinogen Antigen

Blood Health

Optimal range:   149 - 353 mg/dL

Fibrinogen is a soluble protein in the plasma that is broken down to fibrin by the enzyme thrombin to form clots.

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Fibrosis-4 (FIB-4)

Comprehensive Metabolic Panel (CMP): Biomarkers, Benefits, and Results Explained

Optimal range:   0 - 1.33 Score

Noninvasive estimate of liver scarring in HCV and HBV patients, to assess need for biopsy.

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Fibulin

Array 5 Multiple Autoimmune Reactivity Screen, Cyrex Laboratories

Optimal range:   0.4 - 1.3 ELISA Index

ANTIBODIES ASSOCIATED WITH:
This test by itself is not diagnostic for any condition or disease

Atherosclerotic Lesions
Osteoarthritis  

BODY TISSUE:

Joint

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Fig

Array 10 - Multiple Food Immune Reactivity Screen, Cyrex Laboratories

Optimal range:   0.2 - 2.2 ELISA Index

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Finasteride

ZRT Laboratory (Salivary Steroids), ZRT Laboratory

Optimal range:   0 - 5 pg/mL

Finasteride is a 5α-reductase inhibitor used to block the formation of the potent androgen DHT from its precursor, testosterone. It is used to treat benign prostatic hyperplasia as well as male pattern baldness in men and women, and excessive facial or body hair growth in women.

Serum testosterone levels increase as a result of the reduced conversion to DHT, but the increase is not usually outside the normal range

. Treatment with finasteride has been linked with sexual side effects.

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Firmicutes

GI-MAP Interpretive Guide by Diagnostic Solutions, Diagnostic Solutions Laboratory | GI-MAP & Food Sensitivity Tests

Optimal range:   57000000000 - 300000000000 Units

Gram-negative Bacteroidetes and grampositive Firmicutes are bacterial phyla that dominate the entire human digestive tract, including the mouth, nose, throat, and colon.2 An abnormal result in one or both of these phylum suggest imbalanced normal microbes in the GI tract. Further, high Firmicutes and low Bacteroidetes (resulting in a high F/B ratio) suggest microbial imbalance which may be related to increased caloric extraction from food, fat deposition and lipogenesis, impaired insulin sensitivity, and increased inflammation.

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Firmicutes

GI360 stool profile, Doctor's Data

Reference range:   -3, -2, -1, 0, +1, +2, +3

Gram-negative Bacteroidetes and grampositive Firmicutes are bacterial phyla that dominate the entire human digestive tract, including the mouth, nose, throat, and colon.2 An abnormal result in one or both of these phylum suggest imbalanced normal microbes in the GI tract. Further, high Firmicutes and low Bacteroidetes (resulting in a high F/B ratio) suggest microbial imbalance which may be related to increased caloric extraction from food, fat deposition and lipogenesis, impaired insulin sensitivity, and increased inflammation.

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Firmicutes Phylum

Complete Microbiome Mapping (NutriPATH), NutriPATH

Optimal range:   3.5 - 40 %

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