Measures 25-hydroxyvitamin D, the main circulating marker used to assess vitamin D status. It is done to identify deficiency or insufficiency and to place bone/mineral health in context.

Associated / contributor. Low vitamin D has been reported in several nonscarring alopecias, including some patients with diffuse shedding.

Doctors interpret it with symptoms, diet/sun exposure and mineral results. Deficiency may be corrected when clinically indicated.

Assesses a vitamin required for DNA synthesis, neurologic function and normal red-blood-cell production. Deficiency can cause macrocytic anemia and systemic symptoms.

Contextual. Direct evidence linking isolated B12 deficiency to common male pattern hair loss is limited, but B12-related anemia or poor nutrition can coexist with diffuse shedding.

Doctors correlate B12 with CBC indices such as hemoglobin and MCV, dietary history and symptoms. If deficiency is confirmed, the cause and appropriate replacement are addressed.

Measures total T3, an active thyroid hormone. It is mainly used with TSH/T4 to characterize thyroid function when an abnormality is suspected.

Established systemic link. Both overactive and underactive thyroid states can disturb the hair cycle and contribute to diffuse thinning or shedding.

Doctors read T3 together with TSH and T4. Abnormal patterns may lead to repeat testing, free-hormone tests, thyroid antibodies or endocrine evaluation depending on the clinical picture.

Measures total T4, the principal hormone produced by the thyroid gland. It helps characterize thyroid hormone production.

Established systemic link. Thyroid dysfunction may change hair texture, density and cycling; the laboratory pattern matters more than T4 alone.

Doctors interpret T4 with TSH (and often free T4 if needed) to distinguish hypo- from hyperthyroid patterns and decide whether additional thyroid evaluation is required.

Measures thyroid-stimulating hormone from the pituitary. TSH is a sensitive first-line marker for many thyroid disorders.

Established systemic link. Thyroid dysfunction is a recognized cause of diffuse hair changes, making TSH a common part of hair-loss work-ups when indicated.

Doctors use TSH as an anchor result and interpret it with T4/T3, symptoms, medications and prior thyroid history. An abnormal value is not treated based on hair loss alone.

Measures the oxygen-carrying protein inside red blood cells. Low hemoglobin is a core feature of anemia.

Contributor through anemia. Anemia can reduce oxygen delivery and often travels with iron, B12 or other deficiencies that may contribute to diffuse shedding.

Doctors classify the severity of anemia and combine Hb with MCV, MCH/MCHC, RDW, ferritin and B12 to identify the likely cause.

The percentage of blood volume occupied by red blood cells. It usually moves in the same direction as hemoglobin.

Contributor through anemia. A low PCV supports reduced red-cell mass; it is not a hair-loss marker by itself.

Doctors use PCV with hemoglobin and RBC count to confirm an anemia pattern and assess whether dehydration or other factors may be affecting the result.

Counts red blood cells per unit of blood. The count helps separate different anemia patterns.

Contextual to hair loss. Low or abnormal red-cell patterns can point toward anemia or marrow/nutritional issues that may contribute to systemic shedding.

Doctors interpret RBC count with hemoglobin, hematocrit and cell-size indices; the relationship between these values can suggest iron deficiency, thalassemia traits or other causes.

Reports the average size of red blood cells. Low MCV suggests microcytosis; high MCV suggests macrocytosis.

High-value context. Iron deficiency often lowers MCV; B12/folate deficiency can raise it. Both are relevant when investigating diffuse shedding.

Doctors use MCV to classify anemia and decide which follow-up tests are appropriate, such as iron studies, B12/folate assessment or other evaluations.

Estimates the average amount of hemoglobin in each red blood cell.

Contextual. Low MCH commonly accompanies iron-deficient, smaller red cells; this can support a deficiency pattern linked with diffuse shedding.

Doctors interpret MCH with MCV and MCHC rather than alone to characterize red-cell morphology and anemia type.

Estimates the concentration of hemoglobin within red blood cells.

Contextual. A low MCHC can support hypochromic anemia, often seen in iron deficiency. It is not a direct hair marker.

Doctors use MCHC alongside MCV, MCH, RDW and iron studies to refine the likely anemia pattern.

Measures how much red-blood-cell size varies, expressed as a coefficient of variation.

Contextual. A rising RDW can appear with evolving nutrient deficiency or mixed anemia, which can be relevant in diffuse shedding work-ups.

Doctors compare RDW-CV with MCV and ferritin/B12. High variability can suggest more than one red-cell population or an evolving deficiency.

Another measure of variation in red-blood-cell size, expressed as an absolute width.

Contextual. Like RDW-CV, it helps characterize anemia rather than diagnose hair loss.

Doctors use RDW-SD as part of the red-cell pattern, especially when MCV and RDW-CV need additional context.

Counts white blood cells, which respond to infection, inflammation, medications and marrow conditions.

Indirect. Acute or systemic illness can trigger telogen shedding, but WBC is not a hair-loss test and can be normal in hair disorders.

Doctors interpret total WBC with the differential counts and symptoms to decide whether infection, inflammation or hematologic follow-up is needed.

The percentage of circulating white cells that are neutrophils, the main acute bacterial/inflammatory responder.

Indirect. A change may reflect systemic illness that can secondarily affect hair cycling; it does not diagnose a scalp condition.

Doctors interpret the percentage with total WBC and the absolute neutrophil count; percentages can mislead when total counts are abnormal.

The actual number of neutrophils in the blood.

Indirect. Marked infection/inflammation or severe systemic stress can be relevant to telogen shedding; the count itself is not a hair marker.

Doctors often give the absolute count more weight than the percentage when assessing infection risk, inflammation, medicines or marrow function.

The proportion of white cells that are lymphocytes, which are central to adaptive immune responses.

Indirect. Viral illness and immune changes can alter lymphocytes; some systemic illnesses may precipitate diffuse shedding.

Doctors read the percentage with total WBC and the absolute lymphocyte count, and investigate persistent abnormalities in clinical context.

The actual number of lymphocytes in the blood.

Indirect. It provides systemic immune context, not a diagnosis of alopecia.

Doctors use absolute lymphocyte count to assess immune/viral patterns and determine whether a persistent abnormality needs follow-up.

The proportion of white cells that are monocytes, cells involved in inflammation and tissue cleanup.

Indirect. Changes can accompany infection or inflammation but have no specific relationship to common male hair loss.

Doctors interpret the percentage with the absolute monocyte count and the rest of the WBC differential.

The actual number of monocytes in the blood.

Indirect. Persistent elevation can reflect chronic inflammation, infection or recovery states; hair relevance is secondary.

Doctors investigate meaningful persistent abnormalities based on symptoms and the rest of the blood count.

The proportion of white cells that are eosinophils, often associated with allergy, asthma, parasites and some drug reactions.

Indirect / limited. Eosinophils do not diagnose hair loss; they may add context when allergic, parasitic or drug-related illness is suspected.

Doctors compare the percentage with the absolute eosinophil count and the patient’s symptoms before deciding whether additional testing is needed.

The actual number of eosinophils in the blood.

Indirect / limited. It is an immune-context marker rather than a hair-loss marker.

Doctors use the absolute count to judge whether eosinophilia is clinically significant and evaluate allergy, parasitic exposure, medications or other causes as appropriate.

The proportion of white cells that are basophils, a small population involved in allergic and inflammatory signaling.

Indirect / limited. Basophil percentage has no established standalone role in diagnosing common hair loss.

Doctors interpret it as part of the differential; isolated minor shifts are often less important than the overall blood-count pattern.

The actual number of basophils in the blood.

Indirect / limited. It contributes to general hematologic context rather than hair-loss diagnosis.

Doctors consider persistent or marked abnormalities in the context of allergy, inflammation or hematologic conditions.

Counts early granulocyte forms released from bone marrow, which may rise during acute infection, inflammation or marrow stress.

Indirect. A systemic illness severe enough to shift marrow output can also trigger telogen shedding, but IG is not a hair marker.

Doctors use IG with WBC/neutrophils and symptoms to assess whether an acute inflammatory or infectious process needs attention.

The percentage of white cells made up of immature granulocytes.

Indirect. It mirrors marrow response and systemic illness rather than a specific cause of hair loss.

Doctors interpret IG% with the absolute IG count and total WBC; abnormal results are followed according to the broader clinical picture.

Counts immature red blood cells in peripheral blood; they are usually absent or extremely low in healthy adults.

Indirect / not hair-specific. Their presence can signal significant physiologic or marrow stress and deserves medical interpretation.

Doctors evaluate unexpected NRBCs with the full CBC and clinical status; they do not use NRBCs to diagnose hair loss.

Reports NRBCs as a percentage relative to counted blood cells.

Indirect / not hair-specific. It is a hematology context marker, not a hair marker.

Doctors use the percentage with the absolute NRBC count and other CBC abnormalities to decide whether further hematologic evaluation is needed.

Counts platelets, the blood cells involved in clotting and vascular repair.

Very indirect. Platelet abnormalities can reflect systemic illness, deficiency or marrow disorders, but are not a routine cause-marker for male hair loss.

Doctors evaluate low or high platelet counts for bleeding/clotting and systemic causes; hair decisions are not based on platelet count alone.

Measures the average size of platelets; larger platelets are generally younger and more active.

Very indirect. MPV is not a validated hair-loss biomarker.

Doctors interpret MPV with platelet count and clinical context when evaluating platelet production or turnover.

Measures the variability in platelet size.

Very indirect. It adds hematologic detail rather than hair-loss information.

Doctors use PDW with MPV and platelet count if platelet abnormalities need characterization.

Estimates the fraction of blood volume occupied by platelets, analogous to hematocrit for red cells.

Very indirect. It is not used to diagnose hair loss.

Doctors interpret PCT with platelet count/MPV when assessing platelet mass and hematologic patterns.

Estimates the proportion of larger platelets in circulation.

Very indirect. There is no established standalone role in common hair-loss evaluation.

Doctors use PLCR only as supportive platelet information when the platelet count or other indices are abnormal.