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LDL Cholesterol, Serum/Plasma — Substance Concentration

Published: August 9, 2026Updated: August 16, 2026

This blood test measures low-density lipoprotein (LDL) cholesterol, a lipid that contributes to cholesterol buildup in artery walls.

Quick summary

["LDL cholesterol helps assess cardiovascular risk; lower levels are generally preferable for most people."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
96258-9
Short code
LDLc SerPl Mart-Hopk-sCnc
Synonyms
LDLc SerPl Mart-Hopk-sCnc
Category
lipid
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
100
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
calculated-martin-hopkins
CPT
83721
SNOMED
113079007
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

LDL cholesterol is a type of cholesterol carried in the blood. This test measures its concentration in serum or plasma and may be reported in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).

Why might I need this test?

The test is commonly used to evaluate cholesterol levels and cardiovascular risk. It may be ordered for routine screening, during treatment of high cholesterol, or when another type of cholesterol is unexpectedly high.

How is the test performed?

A blood sample is drawn and the serum or plasma is analyzed. Depending on the laboratory, LDL cholesterol may be measured directly or calculated using the results of other cholesterol measurements.

How do I prepare for the test?

Follow your clinician's instructions about fasting. Some LDL measurements are accurate without fasting, while others are interpreted as part of a fasting lipid panel. Unless you are told otherwise, do not stop prescribed medicines or fast for an extended period without guidance.

Reference range

Optimal: <100 mg/dLN/A

Specimen: serum

Fasting for 12-14 hours preferred. Water is permitted. Avoid alcohol for 24 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

LDL cholesterol

Frequently asked questions

Is a fasting blood test required for LDL cholesterol?
Not always. Many LDL measurements can be interpreted without fasting, but your clinician may request a fasting lipid panel for specific reasons. Confirm the instructions before your blood draw.
Why is LDL cholesterol called “bad” cholesterol?
LDL can carry cholesterol into artery walls, where excess cholesterol may contribute to plaque buildup. This is why LDL is considered a major cardiovascular risk factor.
Can lifestyle or medicines change LDL cholesterol?
Yes. Diet, physical activity, weight, smoking, and medications can affect LDL levels. Changes should be discussed with your clinician, especially if you already have a heart condition or other cardiovascular risk factors.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

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 16, 2026. · Read our editorial policy