Evidence-Based Supplement & Herb Guides

Selenium Blood Test Normal Range: Reference Values and Meaning

Understand selenium blood test normal ranges, low and high selenium results, deficiency and toxicity causes, thyroid links, preparation, and safe follow-up steps.

A selenium blood test measures the amount of selenium in your blood, most often in serum or plasma. Selenium is a trace mineral, which...

Serum Folate vs RBC Folate: What Is the Difference?

Serum folate reflects recent folate intake, while RBC folate reflects longer-term folate status. Learn how the tests differ, what low or high results can mean, and how to interpret folate results with B12, CBC, MMA, homocysteine, diet, medications, and pregnancy needs.

Serum folate and RBC folate are two blood tests that look at vitamin B9 status from different angles. Serum folate measures folate circulating in...

Serum Iron Test Normal Range: Reference Values and Meaning

Serum iron normal range, low and high result meanings, iron panel context, preparation tips, and when abnormal iron levels need medical follow-up.

A serum iron test measures the amount of iron circulating in the liquid part of your blood. Most of that iron is attached to...

Serum Magnesium vs RBC Magnesium: Which Magnesium Test Matters More?

Serum magnesium is usually the first and most useful magnesium test, while RBC magnesium can add context in selected chronic cases. Learn how to interpret both tests, common result patterns, and when follow-up matters.

Serum magnesium usually matters more for routine medical care because it is standardized, widely available, and better suited for detecting clinically important low or...

Soluble Transferrin Receptor (sTfR) Test: High sTfR, Iron Deficiency, Anemia, and Results

Understand the soluble transferrin receptor test, what high sTfR can mean, how it helps detect iron deficiency, and how results compare with ferritin, TSAT, and CBC findings.

The soluble transferrin receptor test, often shortened to sTfR, is a blood test that helps show whether the body is struggling to get enough...

TIBC vs Transferrin: What Is the Difference in an Iron Panel?

TIBC and transferrin both help interpret iron panels, but they measure different things. Learn how high or low results relate to iron deficiency, inflammation, liver disease, and iron overload.

TIBC and transferrin are closely related iron tests, but they are not the same measurement. Transferrin is the blood protein that carries iron. TIBC,...

Total Iron-Binding Capacity (TIBC) Test Normal Range: Reference Values and Meaning

Learn the normal range for the TIBC blood test, what high and low total iron-binding capacity mean, and how TIBC fits with ferritin, serum iron, and transferrin saturation.

Total iron-binding capacity, or TIBC, is a blood test that estimates how much iron your blood can carry. It mainly reflects transferrin, the protein...

Transferrin Blood Test Normal Range: Reference Values and Meaning

Learn the normal transferrin blood test range, what high and low transferrin mean, and how transferrin fits with ferritin, TIBC, serum iron, and TSAT.

Transferrin is the main blood protein that carries iron from your digestive tract and iron stores to the bone marrow, where red blood cells...

Transferrin Saturation (TSAT) Normal Range: Reference Values and Meaning

Learn the normal transferrin saturation range, what low or high TSAT means, how it is calculated, and how TSAT fits with ferritin, serum iron, TIBC, and anemia testing.

Transferrin saturation, often shortened to TSAT, is a percentage that shows how much of your iron-carrying protein is currently loaded with iron. It is...

Unsaturated Iron-Binding Capacity (UIBC) Test Normal Range: Reference Values and Meaning

Learn what the UIBC blood test measures, the common normal range, and how high or low UIBC results relate to iron deficiency, iron overload, ferritin, TIBC, and transferrin saturation.

Unsaturated iron-binding capacity, or UIBC, is a blood test that estimates how much extra iron your blood can still carry. It looks at the...

Vitamin A (Retinol) Test Normal Range: Reference Values and Meaning

Learn what a vitamin A retinol blood test measures, common normal ranges, low and high result meanings, deficiency cutoffs, toxicity concerns, preparation tips, and follow-up tests.

The vitamin A blood test measures retinol, the main circulating form of vitamin A in blood. It is usually ordered when a clinician suspects...

Vitamin and Mineral Blood Test Panel: Deficiency, Toxicity, Nutrient Levels, and Results

Learn what a vitamin and mineral blood test panel measures, how to interpret low or high nutrient levels, which markers matter, and when follow-up testing is needed.

A vitamin and mineral blood test panel checks selected nutrients in the blood to look for deficiency, excess, absorption problems, or patterns that may...

Vitamin B1 (Thiamine) Test: Low Thiamine, Deficiency, Normal Range, and Results

Learn what a vitamin B1 thiamine test measures, common normal ranges, low and high result meanings, deficiency symptoms, causes, preparation, and follow-up steps.

A vitamin B1 test checks whether your body has enough thiamine, a water-soluble vitamin needed for energy production, nerve function, heart function, and carbohydrate...

Vitamin B2 (Riboflavin) Test: Low Riboflavin, Deficiency, Normal Range, and Results

Learn what a vitamin B2 riboflavin test measures, normal ranges for plasma, whole blood, and EGRAC, causes of low riboflavin, deficiency symptoms, and follow-up testing.

A vitamin B2 test checks whether your body has enough riboflavin, a water-soluble B vitamin needed for energy production, red blood cell function, antioxidant...

Vitamin B3 (Niacin) Test: Low Niacin, Deficiency, Normal Range, and Results

Learn what a vitamin B3 niacin test measures, what low or high results mean, common normal ranges, deficiency symptoms, pellagra risk, test preparation, and safe follow-up.

Vitamin B3 testing checks whether niacin status is low enough to suggest deficiency or high enough to raise concern for excess intake, usually from...

Vitamin B5 (Pantothenic Acid) Test: Low Pantothenic Acid, Deficiency, Normal Range, and Results

Learn what a vitamin B5 blood test measures, what low pantothenic acid may mean, how normal ranges vary, and how to interpret deficiency or high results.

A vitamin B5 test measures pantothenic acid, a water-soluble B vitamin needed to make coenzyme A, a molecule your body uses for energy metabolism,...

Vitamin B6 (Pyridoxal-5-Phosphate/PLP) Test Normal Range: Reference Values and Meaning

Understand the vitamin B6 PLP blood test normal range, low and high results, symptoms, causes, supplement risks, preparation tips, and follow-up testing.

A vitamin B6 blood test usually measures pyridoxal-5-phosphate, often shortened to PLP or P5P. PLP is the main active form of vitamin B6 in...

Vitamin B7 (Biotin) Test: Low Biotin, Deficiency, Normal Range, and Results

Learn what a vitamin B7 biotin test measures, normal range examples, causes of low biotin, deficiency symptoms, high supplement levels, lab interference, and follow-up testing.

A vitamin B7 test checks biotin status or looks for excess biotin from supplements that may interfere with other blood tests. Biotin is a...

Vitamin B12 and MMA: Interpreting B12 Status Without Overdoing Supplements

Learn how vitamin B12 and MMA results are interpreted together, what high MMA can mean, when supplements help, and how to avoid overdoing B12 replacement.

Vitamin B12 testing can be confusing because a “normal” B12 result does not always prove that cells have enough usable B12, and a low-normal...

Vitamin B12 Blood Test Normal Range: Reference Values and Meaning

Understand the vitamin B12 blood test normal range, low and high B12 results, borderline values, symptoms, causes, and follow-up tests like MMA and homocysteine.

A vitamin B12 blood test measures the amount of cobalamin circulating in your blood. Vitamin B12 helps make healthy red blood cells, supports nerve...