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Dr. Alessandro Giardini
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A set of blood results taken recently has arrived and one of the cholesterol numbers looks higher than expected. Your child feels completely well. You are now trying to work out whether this actually matters.
That scenario plays out in Dr. Alessandro Giardini's clinics every week. In most cases, the numbers turn out to be reassuring once they have been placed in context.
Understanding what each measurement means and where the normal thresholds sit usually in enough to remove a great deal of unnecessary worry.
A standard cholesterol blood test normally reports four values. LDL cholesterol is the one that matters most clinically. It is called bad cholesterol in laymen's terms. It deposits cholesterol into the walls of arteries and drives long-term cardiovascular risk when persistently elevated. HDL cholesterol works in the opposite direction (the good cholesterol), helping to clear cholesterol from arteries. Higher HDL is protective.
Triglycerides are a separate blood fat that rises with dietary sugar, excess weight, and reduced activity. They also vary depending on whether the child fasted before the test. Total cholesterol is simply the sum of all fractions. It can mislead on its own because a high total due to high HDL is a completely different picture from one driven by high LDL.
The thresholds below come from the National Heart, Lung, and Blood Institute guidelines and are widely used in UK paediatric practice. All values assume a fasting sample. Non fasting levels can be more elevated and when testing a fasting level is recommended.
For total cholesterol, the acceptable level is below 4.4 mmol/L, borderline is 4.4 to 5.17 mmol/L, and high is 5.18 mmol/L or above. For LDL cholesterol, acceptable is below 2.85 mmol/L, borderline is 2.85 to 3.34 mmol/L, and high is 3.35 mmol/L or above. HDL cholesterol above 1.17 mmol/L is acceptable; below 1.04 mmol/L is considered low.
Triglyceride thresholds change with age. For children under 10 years of age, acceptable is below 0.85 mmol/L and high is 1.13 mmol/L or above. For those aged ten to nineteen, acceptable is below 1.02 mmol/L and high is 1.47 mmol/L or above.
Dr. Giardini treats these ranges as a starting point. A number sitting just above a threshold line rarely changes management without the broader clinical picture.
Cholesterol levels shift with age, puberty, recent illness, and even whether the child truly fasted. A viral infection can push LDL up transiently. Puberty itself alters lipid metabolism, with LDL typically dipping in early puberty and rising again afterwards. The same child tested six months apart can produce meaningfully different results.
That is why most clinicians avoid drawing conclusions from one borderline lipid profile. Two or three results taken weeks apart reveal the trend far more reliably than any single snapshot.
Most children with mildly elevated cholesterol need nothing more than sensible dietary habits and regular activity. A small proportion, however, have a pattern that warrants specialist review.
LDL consistently above 4 mmol/L is one important signal. A family history of heart attacks or strokes in relatives under 55 (men) or 65 (women) is another. If a parent carries a diagnosis of familial hypercholesterolaemia, each child has a 50 per cent chance of inheriting it. When these features cluster together, Dr. Giardini recommends a comprehensive assessment including repeat fasting lipids and a detailed family history review.
For a full explanation of inherited cholesterol conditions, diagnosis, and treatment options, see the main page on high cholesterol in children.
Below 2.85 mmol/L is considered acceptable. Levels between 2.85 and 3.34 mmol/L are borderline. Anything at or above 3.35 mmol/L is classified as high. These thresholds apply across childhood, though interpretation always considers the individual child's circumstances and family history.
A non-fasting sample is acceptable for initial screening. Triglyceride levels, however, rise substantially after eating and may be unreliable without fasting. When precision matters, a 9 to 12 hour fast with only water gives the most accurate results.
In most cases, no. Borderline results often reflect normal variation, recent illness, or dietary factors. A repeat test after a few weeks usually clarifies the picture. Without a concerning family history, borderline numbers rarely require anything beyond healthy lifestyle habits.
Specialist assessment is appropriate when LDL is persistently above 4 mmol/L, when there is a family history of early heart disease, or when a parent has been diagnosed with familial hypercholesterolaemia. Dr. Giardini sees children across this range at his London clinics and can advise whether further investigation is needed.
Author: Dr. Alessandro Giardini, MD, PhD
Written 09/05/2026