LDL test

Definition

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)

Alternative Names

LDL cholesterol; Low-density lipoprotein LDL cholesterol levels

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:

• Heart disease
• Peripheral artery disease
• Heart attack
• Stroke

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:

• Excessive bleeding
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood buildup under the skin)
• Infection (a slight risk any time the skin is broken)

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 pubmed.ncbi.nlm.nih.gov/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.