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Phospholipid Profile (Lecithin/Sphingomyelin Ratio) in Serum

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

This test measures the ratio of lecithin to sphingomyelin in your blood, often used to assess lung maturity in certain medical contexts.

Quick summary

["Helps evaluate lung development in newborns or specific metabolic conditions in adults."]

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

Key facts at a glance

LOINC
49577-0
Short code
Lecithin MFr Amn
Synonyms
Lecithin MFr Amn
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test to check for lung maturity in premature newborns, as high levels of lecithin can indicate healthy lung development. It may also be used in research or specialized clinical settings to study phospholipid metabolism in adults with certain conditions.

What to Expect Before the Test

No special preparation is needed. You’ll typically provide a blood sample, often drawn from your arm. If you’re a pregnant woman, your provider may discuss timing with you, as this test is most relevant in prenatal care.

What the Results Mean

The ratio reflects the balance of two key phospholipids in your blood. While exact values vary by context, higher ratios may suggest lung maturity or specific metabolic states. Your healthcare provider will interpret results in relation to your clinical situation.

Common Conditions Monitored

This test is primarily associated with assessing fetal lung development in high-risk pregnancies or evaluating phospholipid disorders in adults. It’s not a routine blood test for general health.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Lecithin/Sphingomyelin Ratio (L/S Ratio)

Frequently asked questions

Will this test affect my diet or medications?
No dietary restrictions are typically required, and this test does not usually interact with common medications. Always follow your healthcare provider’s advice for any specific instructions.
How long will I need to wait for my results?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your provider will contact you directly with the findings.
Can I get this test if I don’t have a referral?
This test is often ordered as part of specialized prenatal or research protocols. Check with your healthcare provider to confirm if it’s appropriate for your situation.
  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