Unit Converter
Cholesterol Total
(Total Serum Cholesterol – Sum of All Cholesterol in Lipoprotein Fractions)
Synonyms
- Total cholesterol
- TC
- Serum cholesterol
- Plasma cholesterol
Units of Measurement
- mmol/L
- µmol/L
- mg/dL
- mg/100 mL
- mg%
- mg/L
- µg/mL
Description
Total cholesterol represents the sum of all cholesterol carried by major lipoproteins:
- LDL cholesterol (LDL-C)
- HDL cholesterol (HDL-C)
- VLDL cholesterol (VLDL-C)
- IDL cholesterol
It remains a routinely used biomarker for assessing cardiovascular health and metabolic status. Although LDL-C is the primary therapeutic target, total cholesterol remains a key component of the lipid profile.
Physiological Role
Cholesterol is essential for:
- Cell membrane stability
- Synthesis of steroid hormones (cortisol, sex hormones)
- Vitamin D synthesis
- Bile acid formation
- Myelin structure in the nervous system
Cholesterol is synthesized in the liver, but also absorbed from diet.
Clinical Significance
High Total Cholesterol (Hypercholesterolemia)
Major Causes:
- Diet high in saturated/trans fats
- Familial hypercholesterolemia (FH)
- Metabolic syndrome
- Type 2 diabetes
- Hypothyroidism
- Nephrotic syndrome
- Liver disease (cholestatic)
- Genetic dyslipidemias
- Alcohol excess
Clinical Relevance:
High total cholesterol increases risk of:
- Atherosclerosis
- Coronary artery disease
- Stroke
- Peripheral arterial disease
Low Total Cholesterol
Less common; may indicate:
- Malnutrition
- Hyperthyroidism
- Chronic illness (cachexia)
- Liver failure
- Malabsorption syndromes
- Certain cancers
- Statin or PCSK9 inhibitor therapy
Low cholesterol is usually not harmful unless extremely low.
Reference Intervals & Risk Categories
Reference Range (Adults)
- < 200 mg/dL (< 5.2 mmol/L) → Desirable
- 200–239 mg/dL (5.2–6.2 mmol/L) → Borderline high
- ≥ 240 mg/dL (≥ 6.2 mmol/L) → High
Children
- < 170 mg/dL (<4.4 mmol/L) optimal
- ≥ 200 mg/dL high
Non-fasting Testing
Total cholesterol is minimally affected by fasting status.
Unit Meanings
| Unit | Meaning |
| mmol/L | millimole per liter |
| µmol/L | micromole per liter |
| mg/dL | milligram per deciliter |
| mg% | milligram per 100 mL (same as mg/dL) |
| mg/L | milligram per liter |
| µg/mL | microgram per milliliter |
Diagnostic Uses
1. Cardiovascular Risk Assessment
Total cholesterol is part of:
- Total/HDL ratio
- Non-HDL cholesterol
- ASCVD risk calculator
- Metabolic syndrome screening
2. Monitoring Lipid-Lowering Therapy
Statins, ezetimibe, and PCSK9 inhibitors reduce total cholesterol significantly.
3. Metabolic Disease Workup
- Diabetes
- Obesity
- Thyroid disease
- Genetic dyslipidemias
4. Pediatric Lipid Disorders
Early detection prevents premature ASCVD.
Analytical Notes
- Serum or plasma acceptable
- Affected by liver disease and thyroid dysfunction
- Hemolysis/lipemia may interfere with optical assays
- Direct enzymatic assays used in modern analyzers
- No fasting required unless triglycerides also tested
Clinical Pearls
- Total cholesterol alone is insufficient-ALWAYS evaluate LDL, HDL, TG, and non-HDL cholesterol.
- Very high total cholesterol (>300 mg/dL) strongly suggests familial hypercholesterolemia.
- Non-HDL cholesterol (TC – HDL) is a better predictor of ASCVD risk than total cholesterol.
- In severe illness, total cholesterol often decreases (negative acute-phase effect).
Interesting Fact
About 70–80% of cholesterol is synthesized in the liver, meaning dietary cholesterol contributes less to blood levels than previously believed - the real culprits are saturated fats & genetics.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Lipids & Lipoproteins.
- ACC/AHA Guidelines (2018–2023) - Cholesterol Management.
- NCEP ATP III - Adult Treatment Panel.
- ESC/EAS Dyslipidemia Guidelines.
- IFCC Lipid Measurement Standards.
- Mayo Clinic Laboratories - Total Cholesterol.
- ARUP Consult - Lipid Disorders.