Clinical Chemistry Calculators
Clinical chemistry brings together calculations derived from serum measurements: glucose metabolism, lipids, electrolytes and acid-base balance, liver and muscle enzymes, iron status and hormones. The tools in this category apply published, named formulas for laboratory professionals, clinicians, students and teachers who need to check or teach these calculations.
Glucose metabolism and insulin
Use these to estimate insulin resistance (HOMA-IR) or beta-cell function (HOMA-B) from fasting glucose and insulin. The third tool converts HbA1c into estimated average glucose with the ADAG equation.
Assess insulin resistance from fasting glucose and fasting insulin.
Open calculatorEstimate pancreatic beta-cell function.
Open calculatorConvert HbA1c into estimated average glucose, in mg/dL and mmol/L, with the ADAG equation (2008).
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Lipid panel
Use this to estimate LDL cholesterol with the Friedewald formula from total cholesterol, HDL and triglycerides when LDL was not measured directly.
Estimate LDL with the Friedewald formula (1972) and see non-HDL cholesterol too.
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Electrolytes, osmolality and acid-base
Use these to calculate the anion gap, estimate serum osmolality, or correct sodium for glucose and calcium for albumin. All four combine or adjust analytes measured in the same serum sample.
Calculate the anion gap, with optional potassium and albumin correction (Figge, 1998).
Open calculatorCalculated plasma osmolality from sodium, glucose and urea or BUN.
Open calculatorAdjust serum sodium in hyperglycemia with the Katz (1.6) and Hillier (2.4) factors, side by side.
Open calculatorAdjust total calcium for albumin with the usual form of the Payne adjustment (1973), factor 0.8.
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Enzymes and tissue injury
Use these to relate enzymes measured in the same patient. The AST/ALT (De Ritis) ratio supports liver workups, and the CK-MB/total CK ratio helps trace the source of a raised CK.
Helps assess the origin of liver injury.
Open calculatorShare of CK-MB in total CK (relative index, %).
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Iron status
Use this to calculate transferrin saturation from serum iron and total iron-binding capacity (TIBC).
Assess iron status from serum iron and TIBC.
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Hormones
Use this to calculate free and bioavailable testosterone with the Vermeulen formula from total testosterone, SHBG and albumin.
Free and bioavailable testosterone from total testosterone, SHBG and albumin (Vermeulen).
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Choosing the right calculator
Start from what was measured and the clinical or teaching question. HOMA-IR and HOMA-B take the same inputs, fasting glucose and insulin, but answer different questions: the first estimates insulin resistance, the second estimates beta-cell secretory function. Converting HbA1c with the ADAG equation (2008) puts the result on a glucose scale; it does not replace a measured glucose.
When a direct measurement exists, it takes priority over a calculation. Friedewald LDL (1972) is an estimate, while direct LDL measures the analyte. Calculated osmolality does not replace osmometer measurement, and the difference between the two is the osmolal gap. Albumin-corrected calcium is an approximation, whereas ionized calcium measures the free fraction directly. Corrected sodium and the anion gap help interpret electrolytes already on the report.
Caveats and limitations
Check units before you calculate. Glucose may be reported in mg/dL or mmol/L, insulin in µIU/mL or pmol/L and testosterone in ng/dL or nmol/L, and each calculator shows the unit it expects for every field. Use results from the same sample or from simultaneous draws; pairing tests from different days distorts ratios and indices.
Some formulas depend on how the sample was collected. HOMA assumes fasting glucose and insulin. The Friedewald formula loses accuracy when triglycerides are high and should not be used outside the conditions its authors described. Hemolysis, lipemia and icterus interfere with several analytes and, in turn, with the calculation.
Results are estimates that support laboratory reasoning and teaching. They do not establish a diagnosis and do not replace assessment by a health professional who knows the patient.
Frequently asked questions
When should I use calculated LDL instead of measured LDL?
Friedewald LDL is useful when the lab did not measure LDL directly. It depends on total cholesterol, HDL and triglycerides, and becomes less accurate when triglycerides are high. If a direct LDL result is available, use the measured value.
What is the difference between HOMA-IR and HOMA-B?
Both use fasting glucose and insulin and come from the HOMA model described by Matthews and colleagues in 1985. HOMA-IR estimates insulin resistance; HOMA-B estimates pancreatic beta-cell function.
Why correct calcium for albumin?
Part of serum calcium circulates bound to albumin. When albumin is abnormal, total calcium may not reflect the free, biologically active fraction. The correction is an estimate; ionized calcium measures that fraction directly.
Can calculated osmolality replace measured osmolality?
No. Calculated osmolality accounts for sodium, glucose and urea, while an osmometer captures every solute present. The difference between the two, the osmolal gap, exists precisely to flag solutes the formula leaves out.
A support tool for educational purposes; it does not replace clinical assessment.