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General laboratory information for lab and clinic staff, drawn from the cited literature. It is not medical advice and does not interpret any individual’s result.
Short answer: what is a lipaemic specimen?
A lipaemic (US spelling lipemic) specimen is a serum, plasma or blood sample that looks turbid or milky because lipoprotein particles have accumulated in it. The condition is called lipemia. It matters in the laboratory because the turbidity can distort measurements on photometric and immunoassay analysers. There is no single universal “normal range” for lipemia: each analyser manufacturer reports its own lipaemic index (L-index) scale.
Definition and scope: lipemia, lipaemic, lipemic
Lipaemic, lipemic, lipemia and lipaemia all refer to the same thing: sample turbidity caused by lipoprotein particles (Nikolac, 2014). Chylomicrons, at roughly 70 to 1000 nm, cause most of the turbidity; HDL, LDL and small VLDL particles do not produce lipemic samples. Lipemia is a property of the sample, not a diagnosis. Nikolac describes it as the second most frequent endogenous interference after haemolysis and other specimen-integrity problems, affecting an estimated 0.5 to 2.5% of samples.
How lipemia is detected: visual check, L-index and triglycerides
What is the normal range for lipemia?
There is none that applies across instruments. The L-index scale differs by manufacturer: Beckman uses 0 to 5, Siemens 1 to 6, and Abbott and Roche report continuous values tied to Intralipid concentration. Nikolac gives no numeric action thresholds, and the threshold at which an analyte result is suppressed or flagged is set per assay in each reagent’s package insert. Visual inspection and automated indices also agree only moderately (kappa 0.56 in the review), so laboratories are advised to validate the L-index following CLSI C56-A, run daily quality control, and keep written procedures for detection, removal and reporting.
What does it mean if there is visible fat in a blood sample?
It means the sample is turbid enough to see. Lipemia becomes visible in serum when triglycerides exceed about 3.4 mmol/L, but in whole blood only above about 11.3 mmol/L, so it can go unnoticed before the sample is separated. What the turbidity means for a particular person is a question for their clinician, not something a sample appearance settles.
What causes a lipaemic specimen?
Nikolac separates preanalytical from pathophysiological causes.
- Inadequate fasting is the most common preanalytical cause. Fasting definitions vary by country in the review: 12 h in Croatia, at least 8 h in Italy, 10 to 16 h in Australia. Outpatient samples were about four times as often lipaemic as hospital samples.
- Parenteral lipid emulsions (for example Intralipid): the review cites an interval of about 5 to 6 hours after the infusion in this context.
- Pathophysiological conditions named in the review: multiple myeloma, diabetes mellitus, acute pancreatitis, kidney failure and hypothyroidism.
- False L-index rises can come from paraproteins and Patent Blue V dye, so a high index is not always lipid.
Sample handling steps such as the order of draw and the serum separation tube sit upstream of this problem, but the review attributes lipemia mainly to patient state and fasting, not to tube choice.
How lipemia interferes with results
Lipemic blood and test results: mechanisms with named examples
| Mechanism | What happens | Examples from Nikolac (2014) |
|---|---|---|
| Spectrophotometric | Light scatter; absorbance falls across 300 to 700 nm | Methods reading NAD(P)H at 340 nm are strongly affected |
| Immunoassay | Antibody binding can be blocked, giving falsely high or low results | Direction depends on the assay |
| Non-homogeneity | Lipid layer forms at the top of the tube, so the aliquot taken matters | Electrolytes and metabolites read low from the upper part; polar drugs such as valproic acid and steroid hormones read low from the lower part |
| Volume displacement | Plasma is about 92% water, but lipid can occupy about 25% of a lipemic sample | Flame photometry and indirect potentiometry give falsely low electrolytes; noted at triglycerides above 17 mmol/L |
| Excess glycerol | Pseudo-hypertriglyceridaemia | Apparent triglyceride value is inflated |
The effect also varies by reagent. Creatinine was significantly negatively affected on three manufacturers’ systems; CRP showed no significant influence; for bilirubin, the Siemens diazo method was strongly positively affected, the Roche DPD method strongly negatively affected and the Beckman DPD method hardly affected. The practical point is that an interference statement is only valid for one analyte on one platform. A result that is held or flagged by an autoverification rule on the L-index is following exactly this per-assay logic.
How to fix lipemic blood: removal methods compared
This is the laboratory-side summary of the evidence, not a procedure. Two sources compare how well lipid-clearing methods preserve the analyte being measured.
| Method | What the sources report |
|---|---|
| Ultracentrifugation (108,200 x g) | Recommended by Nikolac; the reference method in Castro-Castro et al. (2018) |
| High-speed centrifugation (10,000 x g, 15 min) | In a 14-analyte multicentre comparison, no analyte exceeded the clinical interference limit against ultracentrifugation; the authors conclude it can replace it |
| LipoClear (polymer-based, followed by a 2,000 x g spin) | Exceeded the limit for total protein, albumin and calcium in the multicentre study; recoveries below 85% for GGT, CK-MB and CRP on Beckman reagents in the review; not acceptable for hydrophobic drugs or hormones |
| 1,1,2-trichlorotrifluoroethane extraction (followed by a 2,000 x g spin) | Exceeded the limit for total protein, calcium and AST in the multicentre study |
| Dilution (2 to 3 fold) | Described as probably the best option for therapeutic drugs (Nikolac) |
Which of these a laboratory may use depends on its own validated procedures and on available equipment such as a high-speed centrifuge. Requirements for documenting that quality control belong to the laboratory’s accreditation framework; see CLIA quality control requirements for the US context.
Common misunderstandings
- “Lipemia has a normal range.” It has manufacturer-specific index scales and per-assay thresholds, not a shared one.
- “Lipemia affects every test equally.” The review shows effects ranging from none (CRP) to strong, reagent-dependent shifts (bilirubin).
- “Any method that clears the sample is equivalent.” The multicentre study shows methods that clear turbidity can still shift specific analytes.
- “A high L-index always means lipid.” Paraproteins and Patent Blue V dye can raise it falsely.
- “Visible turbidity is the only warning.” Whole blood can carry high triglycerides without looking lipemic.
FAQ
What does a lipemic specimen indicate?
On its own, only that the sample contains enough lipoprotein particles to be turbid. The documented causes range from a recent meal or lipid infusion to the conditions listed above, so the cause has to be established by the clinical team, not inferred from the sample.
Is “lipemic plasma” different from lipemic serum?
The definition is the same; the matrix differs. The review discusses serum and plasma together, and the multicentre study covers both.
How can lipemic blood be fixed?
Not at the collection site. Laboratories clear or work around lipemia after separation, using ultracentrifugation, high-speed centrifugation, extraction or dilution, each with the analyte limitations in the table above. Recollection after proper fasting is a clinical decision.
Sources
- Nikolac N. Lipemia: causes, interference mechanisms, detection and management. Biochemia Medica 2014;24(1):57-67. doi:10.11613/BM.2014.008. Read 2026-11-07.
- Castro-Castro MJ et al. Removing Lipemia in Serum/Plasma Samples: A Multicenter Study. Annals of Laboratory Medicine 2018;38(6):518-523. PMC6056396. Read 2026-11-07.
