Cholesterol is one of the most misunderstood measurements in medicine. Most people know that "high cholesterol is bad" — but your cholesterol panel gives you four distinct numbers, each telling a different story about your cardiovascular health.
What Is Cholesterol?
Cholesterol is a fatty substance your body produces naturally. It is essential for building cell membranes, producing hormones, and making vitamin D. The problem is not cholesterol itself — it is when certain types of cholesterol accumulate in the walls of your arteries, narrowing them and increasing the risk of heart attack and stroke.
Cholesterol cannot dissolve in blood. It is carried around by proteins called lipoproteins. The type of lipoprotein carrying the cholesterol determines whether it is helpful or harmful.
LDL: The Number That Matters Most
LDL stands for Low-Density Lipoprotein. It is often called "bad cholesterol" because high LDL levels are directly associated with plaque buildup in artery walls.
- Optimal: Below 100 mg/dL (2.6 mmol/L)
- Near optimal: 100–129 mg/dL
- Borderline high: 130–159 mg/dL
- High: 160–189 mg/dL
- Very high: 190 mg/dL and above
Source: National Cholesterol Education Program, Adult Treatment Panel III (NCEP ATP III), NHLBI/NIH, 2001.
If you have existing heart disease, diabetes, or other cardiovascular risk factors, your doctor will likely target an LDL below 70 mg/dL.
HDL: The Protective Cholesterol
HDL stands for High-Density Lipoprotein. It is called "good cholesterol" because it helps remove LDL from your arteries and transport it to the liver for disposal.
- Low (risk factor): Below 40 mg/dL for men, below 50 mg/dL for women
- Normal: 40–59 mg/dL
- Protective: 60 mg/dL and above
Source: NCEP ATP III At-A-Glance, NHLBI/NIH, 2001. An HDL of 60 mg/dL or above is counted as a negative risk factor.
Higher HDL is generally better. Regular aerobic exercise is one of the most effective ways to raise HDL. Smoking significantly lowers it.
Triglycerides: The Hidden Risk Factor
Triglycerides are a type of fat in your blood that comes primarily from food — especially refined carbohydrates, sugar, and alcohol. High triglycerides combined with low HDL is one of the strongest predictors of heart disease risk.
- Normal: Below 150 mg/dL
- Borderline high: 150–199 mg/dL
- High: 200–499 mg/dL
- Very high: 500 mg/dL and above
Source: NCEP ATP III, NHLBI/NIH, 2001.
Very high triglycerides are also associated with pancreatitis — inflammation of the pancreas — which is one reason a doctor acts quickly on them.
Total Cholesterol: Why It Is the Least Useful Number
Your total cholesterol is simply the sum of all cholesterol in your blood — LDL, HDL, and a portion of triglycerides. A high total cholesterol number could be driven by high HDL (protective) rather than high LDL (harmful). This is why doctors now focus on the individual components and ratios rather than total cholesterol alone.
The Cholesterol Ratio
Your total cholesterol divided by your HDL gives a ratio that many doctors use to assess cardiovascular risk. A ratio below 5:1 is desirable; below 3.5:1 is optimal. A ratio above 6:1 indicates elevated risk.
What Affects Your Cholesterol?
- Diet: Saturated fats (red meat, full-fat dairy, coconut oil) raise LDL. Trans fats raise LDL and lower HDL.
- Exercise: Regular aerobic activity lowers LDL and raises HDL.
- Weight: Being overweight raises LDL and triglycerides.
- Genetics: Familial hypercholesterolaemia is a genetic condition causing very high LDL regardless of diet.
- Medications: Statins, fibrates, and other medications can significantly lower LDL.
- Thyroid function: Hypothyroidism raises LDL. Many doctors check thyroid function when cholesterol is high.
Why these categories are not the whole story
The bands above come from NCEP ATP III, published in 2001, and they are still what most laboratories print beside your result. But guidance has moved on: the 2018 ACC/AHA cholesterol guideline no longer treats a single LDL number as the thing that decides treatment, and instead weighs your overall cardiovascular risk — age, blood pressure, diabetes, smoking and family history — alongside it. So a result can sit in a “borderline” band and matter a great deal for one person and very little for another.
This is also why the range printed on your report is the one that counts. Laboratories choose which classification to print, and two can differ while both are right for the people they serve.
Important: Cholesterol results should always be interpreted by your doctor in the context of your full cardiovascular risk profile — not in isolation. This article is for educational purposes only.