Small Dense LDL
Small dense LDL (sdLDL) refers to a subtype of LDL particles that are smaller and denser than average. A predominance of these small particles is sometimes called 'LDL pattern B,' in contrast to the larger, more buoyant particles of 'pattern A.'
Small dense LDL particles are thought to be more atherogenic than larger ones, they slip more easily into the artery wall, are more prone to oxidation, and linger longer in the bloodstream. Measuring them adds nuance about the quality of your LDL, not just the quantity, and a pattern B profile often travels with high triglycerides, low HDL, and insulin resistance.
A high level of small dense LDL (a pattern B profile) is associated with a greater risk of atherosclerosis and is a common feature of metabolic syndrome and type 2 diabetes. It can signal elevated cardiovascular risk even when your total LDL cholesterol looks unremarkable.
Having predominantly large, buoyant LDL (pattern A) with little small dense LDL is generally considered a lower-risk pattern and is usually not a concern by itself.
Lower small dense LDL is generally preferable, and a pattern A profile is more favorable, but there is no single universal cutoff, so interpret your result with a clinician alongside your triglycerides, HDL, and overall metabolic and cardiovascular risk. This is a specialized test not found on standard panels, typically used to refine risk assessment.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.