Ldl Cholesterol

Published: July 31, 2026Updated: August 10, 2026

A blood test that measures the amount of low-density lipoprotein (LDL) cholesterol in your blood, often called the 'bad' cholesterol.

Quick summary

{"LDL cholesterol is known as 'bad' cholesterol because high levels can lead to plaque buildup in arteries","The test is typically done after fasting for 9-12 hours","Normal LDL levels are below 100 mg/dL for optimal heart health","Results help assess risk for heart disease and stroke","Lifestyle changes or medication may be recommended based on results"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 10, 2026Editorial policy

Key facts at a glance

LOINC: 13457-7
Short code: LDL-C
Synonyms: —
Category: lipid
Sample: serum
Container: Serum Separator Tube (SST) or Plain Red Top Tube
Units: mg/dL
Ref low: 100
Ref high: 129
Critical range: 50 mg/dL – 190 mg/dL
Fasting: true
Population: adult
Sex: all
Age range: 2–99 years
Method: enzymatic-selective
CPT: 83721
SNOMED: 44030008
Specimen volume: 3-5 mL
Stability: Room temperature: 24-48 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 3 months
Hemolysis max: 50
Lipemia max: 300
Icterus max: 20
TAT: 1–4 hours

What is this test?

The LDL cholesterol test measures the level of low-density lipoprotein cholesterol in your blood. LDL is often called 'bad' cholesterol because it can build up on the walls of your arteries, forming plaque that narrows and hardens the arteries—a condition called atherosclerosis. This process increases your risk of heart disease, heart attack, and stroke.

During the test, a healthcare professional will draw a blood sample from a vein in your arm. You will typically need to fast for 9-12 hours before the test, only drinking water. The blood sample is then sent to a laboratory for analysis.

Why is it important?

Monitoring LDL cholesterol levels is crucial for maintaining cardiovascular health. High LDL levels often have no symptoms, so regular testing is the only way to know if your cholesterol is too high. Your doctor uses this information to determine your risk of heart disease and decide on treatment options, which may include lifestyle changes or cholesterol-lowering medications.

How to prepare?

To prepare for the LDL cholesterol test: fast for 9-12 hours before the test (only water is allowed), avoid alcohol for 24 hours before the test, inform your doctor about all medications you're taking, and stay hydrated by drinking plenty of water. Follow any specific instructions given by your healthcare provider.

Reference range

< 100 (optimal)mg/dL

Specimen: serum

Patient must fast for 9-12 hours prior to sample collection. Water consumption is encouraged during fasting period. Avoid alcohol for 24 hours before testing. Maintain regular diet for 2-3 weeks prior to testing. Avoid vigorous exercise 24 hours before collection. Certain medications may affect results - consult with physician regarding medication adjustments.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Short name

LDL-C

Part of panels

cardiovascular-screening-basic cardiac-panel lipid-panel-extended lipid-panel diabetes-risk-screening diabetes-comprehensive-management cardiovascular-comprehensive male-cardiovascular-risk male-basic-health-screen female-basic-health-screen health-check-basic health-check-executive male-comprehensive-health female-comprehensive-health elderly-comprehensive-health health-check-comprehensive

Frequently asked questions

How often should I have my LDL cholesterol tested?

Adults should have their cholesterol checked at least once every 4-6 years. However, your doctor may recommend more frequent testing if you have high cholesterol, heart disease, diabetes, or other risk factors. People with existing heart conditions may need testing every 1-2 years or as directed by their healthcare provider.

Can I lower my LDL cholesterol through diet and exercise?

Yes, lifestyle modifications can significantly lower LDL cholesterol. Eating a heart-healthy diet low in saturated fats and trans fats, increasing fiber intake, exercising regularly (at least 150 minutes per week), maintaining a healthy weight, and quitting smoking can all help reduce LDL levels. Some people may also need medication in addition to lifestyle changes.

What happens if my LDL cholesterol is too high?

If your LDL cholesterol is high, your doctor will work with you to develop a treatment plan. This may include dietary changes, increased physical activity, weight management, and possibly cholesterol-lowering medications such as statins. The goal is to lower your LDL levels to reduce your risk of heart disease and stroke.

Do I need to fast before the LDL cholesterol test?

Traditional LDL cholesterol testing requires fasting for 9-12 hours. However, recent guidelines suggest that non-fasting tests may be acceptable for some patients. Your doctor will provide specific instructions based on your individual situation and the specific tests being performed.

What is the difference between LDL and HDL cholesterol?

LDL (low-density lipoprotein) is often called 'bad' cholesterol because it can build up in artery walls. HDL (high-density lipoprotein) is called 'good' cholesterol because it helps remove excess cholesterol from the bloodstream and carries it back to the liver for processing. Having high HDL and low LDL levels is ideal for heart health.

Sources

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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy