LDL to HDL ratio = LDL cholesterol ÷ HDL cholesterol, both in the same units.
The lipoprotein ratio review cited on this page sets risk levels for people without heart disease above 3.5 in men and above 3.0 in women. Its suggested targets for that group are below 3.0 for men and below 2.5 for women. For people who already have heart disease, the review's risk levels drop to above 3.0 for men and above 2.5 for women.
A ratio under the target does not mean heart risk is low, and a ratio above the risk level does not mean heart disease is present. Age, blood pressure, smoking, diabetes and family history all sit alongside the ratio in a full risk estimate, which a clinician puts together.
The two inputs matter on their own as well. The ATP III report treats LDL below 100 mg/dL as optimal and 160 or above as high, and HDL below 40 mg/dL as low. The same ratio can come from very different pairs of numbers, and those pairs are read differently.
Anything that raises LDL or lowers HDL pushes the ratio up. Diet pattern, excess body weight and physical inactivity tend to raise LDL and lower HDL over weeks to months, and smoking tends to lower HDL. Weight loss and regular aerobic activity tend to move both in a helpful direction.
The ATP III report lists conditions that can raise LDL, including an underactive thyroid, some kidney conditions and obstructive liver disease. It also names medicines that can raise LDL or lower HDL, such as progestins, anabolic steroids and corticosteroids. Statins and other lipid medicines lower LDL, so a ratio taken on treatment reads differently from one taken off it.
Because LDL is often calculated from total cholesterol, HDL and triglycerides, a change in triglycerides can move the calculated LDL and therefore the ratio, even when nothing else has changed. It helps to check whether your report says calculated or direct LDL, and to compare like with like across panels.
A ratio that is well above earlier panels is worth repeating under similar conditions before reading much into it, away from a recent illness, a crash diet or a big change in alcohol. If the LDL on the report was calculated and the panel was not fasting, a fasting repeat can make the LDL figure more dependable.
Ratios move slowly with lifestyle change, so a recheck after a few months of steady change usually tells you more than one within days. When a clinician has started or changed lipid treatment, they set the recheck interval, and that schedule comes first.
A ratio above the risk level for your sex, particularly alongside smoking, high blood pressure, diabetes or a family history of early heart disease, is worth discussing with a clinician rather than tracking on your own. A sudden large jump between two panels with no obvious reason is also worth raising.
Most labs calculate LDL rather than measure it, and the ratio inherits any error in that estimate. A 2013 study by Martin and colleagues in more than a million lipid profiles found the Friedewald equation tends to underestimate LDL when LDL is low and triglycerides are high, which would pull the ratio down too.
The ratio leaves out the cholesterol carried in VLDL and other triglyceride-rich particles. In people with high triglycerides, the LDL to HDL ratio can look reassuring while the total cholesterol to HDL ratio and non-HDL cholesterol look less so. That is one reason a clinician rarely reads this ratio without the rest of the panel.
Like any ratio, it hides the size of the inputs. It says nothing about particle number, lipoprotein(a) or LDL particle size, and the risk levels come from adult population studies, not from children, pregnancy or rare inherited lipid disorders. Those need separate tests or a specialist read.
Take an LDL of 130 mg/dL and an HDL of 48 mg/dL from the same panel. The formula is LDL divided by HDL, so 130 divided by 48 gives 2.708, which the calculator rounds to 2.7. The units cancel out, so the result would be the same in mmol/L as long as both values use that unit.
For a man without heart disease, 2.7 is below the review's risk level of 3.5 and also below its target of 3.0. For a woman without heart disease, the same 2.7 is below the risk level of 3.0 but above the target of 2.5. The same ratio lands in a different spot depending on sex.
Now look at the inputs. An LDL of 130 mg/dL sits in the ATP III borderline high band of 130 to 159, and an HDL of 48 is above the low cut-off of 40. A clinician would read the ratio with total cholesterol, triglycerides and the person's other risk factors before saying what it means.
If the same person's LDL were 160 with HDL unchanged, 160 divided by 48 gives 3.33, which rounds to 3.3. That would sit above the targets for both sexes and above the women's risk level. It shows how a rise in LDL alone can carry the ratio across a target.
The lipoprotein ratio review on this page found that both the LDL to HDL ratio and the total cholesterol to HDL ratio had greater predictive value for heart risk than single lipid values, particularly LDL on its own. Its argument is that a ratio captures the balance between particles that deposit cholesterol and the HDL that helps carry it away.
Between the two ratios, the Quebec Cardiovascular Study in men found the total cholesterol to HDL ratio was the more useful index. Lemieux and colleagues linked this to the fact that the total to HDL ratio also reflects the cholesterol in triglyceride-rich particles, which the LDL to HDL ratio does not capture.
Non-HDL cholesterol and apolipoprotein B are other ways to count the particles linked with plaque. In practice a clinician reads the LDL to HDL ratio alongside these rather than on its own, and pays closest attention when they disagree. Apolipoprotein B needs its own test, while non-HDL comes free with a standard lipid panel.
The Heart health panel measures the values this calculator uses. Related: ldl cholesterol, hdl cholesterol, ldl hdl ratio.
For people without heart disease, the review cited here set targets below 3.0 for men and 2.5 for women.
No, as long as both values are in the same unit.
The review found the LDL to HDL and total to HDL ratios had greater predictive value than LDL alone. A clinician reads them together.