My ApoB went down 8 points. Is that real?
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Maybe, but you can’t tell yet. Two ApoB tests can differ by about 15% with nothing changed, because your body moves about 6% between tests and the lab adds 5 to 6% more. At 100, a drop has to pass about 15 points to be probably real and about 23 to be clear. An 8 point drop is inside the noise.
What we’d do
Don’t celebrate or panic over one result. Keep doing whatever you changed, and retest at the same lab 6 to 12 weeks later. For a steadier answer, have two draws a few days apart at each end and average them, which shrinks the band to about 11% and 17%. If the trend keeps going the same way over two or three retests, believe it.
From 104 to 96 is 8 points, 7.7%. Can’t tell yet.
The shaded band is about 15% either side of 104, from 88 to 120. A second result inside it could be the same blood on a different day.
How big a change has to be
Statisticians call this the reference change value. It takes how much your own ApoB wobbles, about 6.4% in a 1992 study of patients tested on three visits, and how much the lab wobbles, 5 to 6% in the College of American Pathologists survey of labs, and asks how far apart two results would land by chance.
| Stamp | Change needed | At 100 | At 120 |
|---|---|---|---|
| Can’t tell yet | under about 15% | under 15 points | under 18 |
| Probably real | about 15% | 15 | 18 |
| Real change | about 23% | 23 | 28 |
“Probably real” means a gap that big turns up by chance only about 1 time in 5. “Real change” means about 1 time in 20.
Three examples
| First | Second | Change | Stamp |
|---|---|---|---|
| 104 | 96, eight weeks later | down 8, 7.7% | Can’t tell yet |
| 120 | 95 | down 25, 21% | Probably real |
| 130 | 98 | down 32, 25% | Real change |
It’s like a bathroom scale that drifts a pound or two. Losing a pound in a week might be the scale. Losing ten over two months is you.
Why ApoB is steadier than LDL
ApoB is measured directly. The LDL on most reports is worked out from three other numbers, and each one brings its own wobble. For LDL, a change has to pass about 29% to be clear, against about 23% for ApoB.
People differ, too. When researchers tested 20 healthy adults four times, two weeks apart, the group’s ApoB varied about 6 to 7%, with “considerable variation” from person to person. Some people’s numbers swing more than others’.
What else can move it
A real change isn’t always the one you made. Starting or changing a cholesterol medicine is the most likely cause of a big drop. The 2026 guideline lists rapid weight loss among the causes of high LDL, and in women ApoB jumps in the year either side of the last period. Retest less than 4 weeks after a change and you’ll mostly see noise. Did my ApoB really change? does the math on your own two results.
5 sources
- Kafonek SD, Derby CA and Bachorik PS, Biological variability of lipoproteins and apolipoproteins in patients referred to a lipid clinic, Clinical Chemistry, 1992pubmed.ncbi.nlm.nih.gov
- Marcovina SM, Gaur VP and Albers JJ, Biological variability of cholesterol, triglyceride, low- and high-density lipoprotein cholesterol, lipoprotein(a), and apolipoproteins A-I and B, Clinical Chemistry, 1994pubmed.ncbi.nlm.nih.gov
- Soffer DE, Marston NA, Maki KC and others, Role of apolipoprotein B in the clinical management of cardiovascular risk in adults: an Expert Clinical Consensus from the National Lipid Association, Journal of Clinical Lipidology, 2024pmc.ncbi.nlm.nih.gov
- Blumenthal RS, Morris PB, Gaudino M and others, 2026 ACC/AHA guideline on the management of dyslipidemia, JACC, 2026doi.org
- Matthews KA and others, Are changes in cardiovascular disease risk factors in midlife women due to chronological aging or to the menopausal transition?, Journal of the American College of Cardiology, 2009pubmed.ncbi.nlm.nih.gov
