How to calculate cholesterol
What are normal cholesterol levels?
Cholesterol and triglycerides are the fats our organism produces most of, and their function is fundamental to several physiological processes.
- Cholesterol is essential to the synthesis of vitamin D and other substances, and is part of our cell membranes and various tissues.
- Triglycerides are an important source of energy for our organism.
Levels of these lipids can rise when your diet contains too many animal-based foods: foods rich in saturated fats (like meat, butter, cold cuts), foods high in trans fats (like margarine, crackers, cookies and chips), carbohydrates and alcohol.
Cholesterol moves through the body thanks to special proteins, called lipoproteins.
- Low Density Lipoproteins (LDL) transport cholesterol to all the organs; the cholesterol associated with these lipoproteins, is known as LDL cholesterol, or, more informally, “bad cholesterol”.
- High Density Lipoproteins (HDL) remove excess cholesterol so that it will be eliminated; the cholesterol associated with HDL is also called “good cholesterol”.
The reason why LDL cholesterol is termed “bad” is due to the fact that at high levels, it can accumulate and form agglomerations that can obstruct the walls of blood vessels.
The following are among the factors that can contribute to an increase in cholesterol levels:
- overweight or obesity,
- lack of physical activity,
High cholesterol is not associated with specific symptoms, but it can be monitored through simple periodic blood tests.
The concentration of cholesterol can be measured with a laboratory test known as the “lipidic profile”.
To construct a lipidic profile, which verifies levels of cholesterol and triglycerides, several parameters are calculated, specifically:
- total cholesterol, the sum of all cholesterol,
- HDL cholesterol (high density cholesterol),
- LDL cholesterol (low density cholesterol),
- non-HDL cholesterol (total cholesterol minus HDL cholesterol),
Total cholesterol, HDL cholesterol and triglycerides are measured in milligrams per deciliter (mg/dl) or in millimoles per liter (mmol/l).
Lipidic profile reference values for adults include:
- total cholesterol: values <200 mg/dl are considered “desirable”,
- LDL cholesterol: values <100 mg/dl are considered “desirable”,
- HDL cholesterol: 40-50 mg/dl*, values >50 mg/are considered “high”, while levels <40 mg/dl are “low”,
- non-HDL cholesterol: values <120 mg/dl are considered “healthy”,
- triglycerides: values ≥150 mg/are considered “high”.
*levels of HDL cholesterol vary depending on sex: ≥40 mg/dl for men and ≥ 50 mg/dl for women.
It is also important to consider the ratio between lipoproteins, the so-called “atherogenic indices”, in particular the relationship between total cholesterol / HDL cholesterol and between LDL cholesterol / HDL cholesterol.
How do you calculate cholesterol?
The values of LDL cholesterol have long been determined using the Friedewald formula:
LDL cholesterol (mg/dl) = total cholesterol (mg/dl) – HDL cholesterol (mg/dl) – [triglycerides (mg/dl)/5]
However, this formula is less precise as levels of triglycerides increase.
At what age and at which intervals should you be screened to check your lipidic profile?
- Young patients (under 19): screening begins between 9 and 11 years of age and should be repeated every 5 years.
- Adults (over 20): screenings every 5 years for younger patients. Men between 45 and 65 and women between 55 and 65 should have a screening done every 1 or 2 years.
If your cholesterol levels are high, after examining the test results your physician will suggest the best strategy to adopt in order to lower them and will calculate the probability of your developing cardiovascular problems in the next 10 years.
A healthy lifestyle is fundamental for controlling cholesterol
Adopting healthy changes in your lifestyle, including a healthy diet, physical activity, maintaining a healthy body weight, giving up bad habits like smoking and managing stress contributes to preventing an increase in cholesterol levels .
A diagnosis of high cholesterol will be evaluated by your doctor based on your medical history, your family’s medical history and a physical exam, or if your LDL cholesterol levels are constantly high over repeated lipidic profile tests.
- If your levels of cholesterol are outside the recommended boundaries for your age and sex, your doctor may recommend changes in your lifestyle aimed at lowering or controlling high cholesterol and prescribe another lipidic profile test.
If necessary, your doctor can request more specific tests in order to see whether the increase in cholesterol is due to other medical conditions.
In the case that changing your lifestyle is not sufficient to lower or control cholesterol levels, your physician may also prescribe a pharmaceutical treatment based on the assumption of substances whose action lowers cholesterol levels, like statins.
- Istituto Superiore di Sanità (ISS). Prevenzione e stili di vita. Disponibile al link: http://www.cuore.iss.it/prevenzione/prevenzione.asp. Ultimo accesso: Luglio 2019
- National Institute of Health- Your guide to lowering your cholesterol with TLC. Disponibile al link:
- Istituto Superiore di Sanità (ISS)- Epicentro. Disponibile al link: https://www.epicentro.iss.it/colesterolo/. Ultimo accesso: Luglio 2019
- Millán J, Pintó X, Muñoz A, et al. Vasc Health Risk Manag. 2009;5:757-65.
- ESC/EAS Guidelines for the Management of Dyslipidaemias. European Heart Journal. 2016;37: 2999–3058
- Schaefer EJ, Tsunoda F, Diffenderfer M, et al. The Measurement of Lipids, Lipoproteins, Apolipoproteins, Fatty Acids, and Sterols, and Next Generation Sequencing for the Diagnosis and Treatment of Lipid Disorders. South Dartmouth (MA): MDText.com, Inc.; 2000-.
- National Institute of Health (NIH) – National Heart, Lung, and Blood Institute (NHLBI). High Blood Cholesterol. Disponibil al link: https://www.nhlbi.nih.gov/health-topics/high-blood-cholesterol. Ultimo accesso: Luglio 2019
- National Health Service (NHS). High cholesterol. Disponibile al link: https://www.nhs.uk/conditions/high-cholesterol/. Ultimo accesso: Luglio 2019