LDL test
LDL cholesterol; Low-density lipoprotein LDL cholesterol levels
The low-density lipoprotein (LDL) test is a blood test to measure the amount of LDL cholesterol in your blood. LDL is a type of fat (lipid) in your blood.
LDL is called "bad" cholesterol because it can build up and form fatty deposits (plaques) in the walls of your arteries.
The LDL test is often done as part of a lipid profile, which measures other fats in your blood:
- Total cholesterol
- HDL cholesterol
- Triglycerides
- Very low-density lipoprotein cholesterol (VLDL cholesterol)
Maybe you've been eating fast food more often than you should, or you're not getting your recommended two-and-a-half hours of exercise each week. Or, it could be that you smoke, or your blood pressure is too high. Well, for whatever reason, you may be concerned about your risk of getting heart disease. Well, a few tests can help you learn that risk, so you can start making healthy lifestyle changes to reduce it. A coronary risk profile is a group of blood tests that measure your cholesterol and triglyceride levels. Why is it important to know these levels? Because if you have too much of these substances in your blood from eating foods like burgers and French fries, they can clog your arteries. Eventually your arteries can become so clogged that you'll have a heart attack or stroke. Men should have their cholesterol tested by the time they're 35. Women should have it checked by age 45. If you have a condition like diabetes, heart disease, stroke, or high blood pressure, have your cholesterol checked now, no matter what your age. To measure your cholesterol, your doctor will give you a blood test. If you're also having your triglyceride level checked, you may be told not to eat or drink anything for 8 to 12 hours before the test. Depending upon your heart risk, the doctor may measure just your total cholesterol level, or your total cholesterol along with your LDL, or bad cholesterol, HDL, or good cholesterol, and triglycerides. If you're of average risk of getting heart disease, your goal is to have total cholesterol of less than 200 milligrams per deciliter, LDL cholesterol lower than 130 milligrams per deciliter, HDL cholesterol higher than 40 milligrams per deciliter if you're a man, or 50 if you're a woman -- the higher the better, and triglycerides of less than 150 also, the lower the better. Although some illnesses, like arthritis, can raise your cholesterol level, generally having high cholesterol means that you're at increased risk for heart disease and stroke. It's a sign you need to work harder to keep your heart healthy. If your cholesterol levels are normal, that's great! That means that you're eating right, you're exercising, and you're taking good care of your health. You don't need to have another cholesterol test for about five years. But if your cholesterol level is high, or you've already got heart disease, high blood pressure, or diabetes, you'll need to have your cholesterol levels checked more often. Keeping close tabs on your cholesterol and triglyceride levels is one way that you can take charge of your health, and change it for the better.
Cholesterol is a soft, waxy substance that is present in all parts of the body including the nervous system, skin, muscle, liver, intestines, and heart. It is made by the body and obtained from animal products in the diet. Cholesterol is manufactured in the liver and is needed for normal body functions including the production of hormones, bile acid, and Vitamin D. Excessive cholesterol in the blood contributes to atherosclerosis and subsequent heart disease. The risk of developing heart disease or atherosclerosis increases as the level of blood cholesterol increases.
Cholesterol is a waxy, fat-like material that is found in all parts of the body. It comes from two sources: our liver produces it, and we consume it in animal products.
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
How the Test is Performed
A blood sample is needed. Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand.
How to Prepare for the Test
You should not eat for 9 to 12 hours before the test.
Alcohol and some medicines can interfere with blood test results.
- Make sure your health care provider knows what medicines you take, including over-the-counter medicines and supplements.
- Your provider will tell you if you need to stop taking any medicines before you have this test.
- Do not stop or change your medicines without talking to your provider first.
How the Test will Feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the Test is Performed
LDL cholesterol is usually measured together with other blood fats. Often it is done to help determine your risk of developing heart disease.
High LDL increases your risk for:
Normal Results
You want your LDL to be low. In general, lower is better.
Your LDL is always considered to be too high if it is 190 mg/dL (4.92 mmol/L) or higher.
General targets for children are less than 110 mg/dL (2.85 mmol/L) (lower numbers are better).
Levels from 70 to 189 mg/dL (1.81 to 4.90 mmol/L) are most often considered too high if:
- You have diabetes and are between ages 40 to 75
- You have diabetes and a high risk of heart disease
- You have a medium or high risk of heart disease
- You have heart disease, history of a stroke, or poor circulation to your legs
In these circumstances, your provider will often recommend medicine to lower your LDL cholesterol level.
Health care providers have traditionally set a target level for your LDL cholesterol if you are being treated with medicines to lower your cholesterol.
- Some newer guidelines now suggest that providers no longer need to target a specific number for your LDL cholesterol. Higher strength medicines are used for the highest risk patients.
- However, some guidelines still recommend using specific targets, including lowering LDL to less than 55 mg/dL in very high-risk patients.
Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
A higher-than-normal LDL may be due to:
- Eating a diet high in saturated fats
- Lack of physical activity
- Being overweight or having obesity
- Diabetes
- Metabolic syndrome
- Certain medicines
- Underactive thyroid gland (hypothyroid)
- Disorder passed down through families in which there are high amounts of cholesterol and triglycerides in the blood (familial combined hyperlipidemia)
- Kidney or liver disease
If your LDL level is high, your provider may recommend changes in your lifestyle such as:
- Eating a healthy diet
- Losing weight (if you are overweight or have obesity)
- Getting regular exercise
- Quitting smoking
- Avoiding alcohol
You may also need medicine to lower your LDL levels if you have diabetes or are at risk of heart disease. While taking medicines to lower your LDL level, you should continue the lifestyle changes.
Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
Considerations
Certain medicines, pregnancy, infection, and some medical conditions can affect test results.
References
Bredefeld CL, Lau R, Hussain MM. Lipids and dyslipoproteinemia. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 18.
Genest J, Mora S, Libby P. Lipoprotein disorders and cardiovascular disease. In: Libby P, Bonow RO, Mann DL, Tomaselli, GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 27.
Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the management of blood cholesterol: a report of the American College of Cardiology/American Heart Association Task Force on clinical practice guidelines. Circulation. 2019;139(25):e1082-e1143. PMID: 30586774
Mora S, Libby P, Ridker PM. Primary prevention of cardiovascular disease. In: Libby P, Bonow RO, Mann DL, Tomaselli, GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 25.
Robinson JG. Disorders of lipid metabolism. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 190.
Version Info
Last reviewed on: 7/25/2024
Reviewed by: Michael A. Chen, MD, PhD, Associate Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
