Total Cholesterol

What is TC?

Total cholesterol is the sum of the cholesterol carried by every lipoprotein class in a blood sample — LDL, HDL, VLDL, intermediate-density particles and, in a non-fasting sample, chylomicron remnants. It is the oldest and simplest lipid measurement, and most of its value today lies in what it is made of: the same total can conceal a favourable or an unfavourable balance between atherogenic particles and HDL, which is why a lipid panel reports the fractions alongside it.

What is TC made of, and where does it come from?

In most adults roughly two-thirds of total cholesterol travels in LDL, about a quarter in HDL, and the remainder in VLDL and other triglyceride-rich particles. Chemically, most of it circulates as cholesteryl esters in the particle core, with a smaller share as free cholesterol in the surface layer; the laboratory assay hydrolyses the esters and measures both forms together, which is what the word 'total' refers to.

What does TC do in the body?

Cholesterol is a structural component of every cell membrane and the raw material for steroid hormones, bile acids and vitamin D. The liver makes most of it and sets the blood level by exporting VLDL, which matures into LDL, and by clearing LDL through its receptors; food contributes less than most people assume, because intestinal absorption is limited and hepatic synthesis adjusts to compensate. Total cholesterol predicts cardiovascular risk in populations largely because LDL-C dominates it: in the 2007 Prospective Studies Collaboration analysis of 61 cohorts, each 1 mmol/L lower total cholesterol was associated with about half the ischaemic heart disease mortality at ages 40-49, and about a sixth lower at ages 70-89.

What does a high TC mean?

A high total cholesterol usually means a high LDL-C, and the risk attached to it is the risk of LDL: more cholesterol-carrying particles entering the artery wall over more years. The exception is a total pushed up by an unusually high HDL-C, which carries a different meaning, so the split is read before the total is interpreted. The 2019 ESC/EAS guideline uses total cholesterol as an input to risk scores such as SCORE but sets treatment goals on LDL-C and non-HDL-C, not on the total; the 2018 AHA/ACC guideline likewise anchors decisions on LDL-C.

Common causes:

• A dietary pattern high in saturated fat — butter, fatty meat, palm and coconut oil — and, in some people, in dietary cholesterol.
• Familial hypercholesterolaemia, an inherited LDL-receptor defect. Suspected when the total is very high from a young age or heart disease runs early in the family.
• Untreated hypothyroidism, which slows LDL clearance and is fully reversible once treated.
• Nephrotic syndrome, cholestatic liver disease, and medications such as corticosteroids, ciclosporin, thiazide diuretics and some retinoids.
• The menopausal transition, across which total and LDL cholesterol rise by roughly 10% as oestrogen falls.
• An unusually high HDL-C, which raises the total without adding atherogenic particles.

What does a low TC mean?

A low total cholesterol is usually unimportant, and when it reflects a low LDL-C it is generally favourable — no level has been identified below which lower LDL-C stops benefiting the heart. The exceptions are falls that happen without any change in diet or medication: total cholesterol drops in hyperthyroidism, malabsorption, malnutrition, advanced liver disease, chronic inflammation and some cancers, and for several weeks after any acute illness or operation. An unexplained fall is therefore a reason to look at the whole picture rather than a result to celebrate.

Common causes:

• Lipid-lowering treatment or a deliberate dietary change doing what it was meant to.
• Hyperthyroidism, which speeds LDL clearance.
• Malabsorption — coeliac disease, pancreatic insufficiency, bowel surgery — or general malnutrition.
• Advanced liver disease, chronic inflammation, or the weeks following an acute illness or heart attack.
• Rare inherited disorders of apolipoprotein B such as hypobetalipoproteinaemia.

What moves TC apart from disease?

Posture and tourniquet time at the blood draw raises it

Standing concentrates lipoproteins by around 5-10% compared with lying down, and a tourniquet left on for more than a minute does the same locally. Blood drawn seated after several minutes of rest is the standard against which reference values were set.

Pregnancy raises it

Total cholesterol rises by roughly 30-50% by the third trimester as a normal part of pregnancy and returns to baseline over the weeks after delivery. A result from this period says little about the usual level.

Recent acute illness, surgery or heart attack lowers it

Any significant inflammatory episode lowers total cholesterol for several weeks, so a value taken in hospital or shortly after an infection can look reassuringly normal while the usual level is higher. Lipids drawn within 24 hours of a heart attack are the accepted exception, because they still reflect the pre-event state.

Season and ordinary day-to-day variation either direction

Total cholesterol runs a few percent higher in winter than in summer, and within-person biological variation is around 5-6% even under identical conditions. A change smaller than about 10% between two tests is within the noise and does not by itself show that anything has changed.

Medications either direction

Oral contraceptives and other oestrogens, corticosteroids, thiazide diuretics, ciclosporin, isotretinoin and some antiretrovirals raise total cholesterol; statins, ezetimibe, bile-acid sequestrants and PCSK9 inhibitors lower it. A change that coincides with a new prescription is more likely to be the prescription than the diet.

Fasting either direction

Total cholesterol changes by only about 0.2 mmol/L after an ordinary meal, which is why the 2016 EAS/EFLM joint statement accepts non-fasting samples for routine lipid testing. The fraction that does move after eating is triglycerides, so a non-fasting panel alters the calculated LDL-C more than it alters the total.

Which other tests are read together with TC?

LDL Cholesterol same panel

LDL-C is the fraction of total cholesterol that drives atherosclerosis and the one guidelines set targets on. A high total with a normal LDL-C and a low total with a high LDL-C are both possible, and only the LDL-C tells you which situation you are in.

HDL Cholesterol read as a ratio

Subtracting HDL-C from total cholesterol gives non-HDL cholesterol, which captures every atherogenic particle in one number and is a secondary treatment goal in the 2019 ESC/EAS guideline. The total-to-HDL ratio serves a similar purpose in several risk calculators.

Triglycerides same panel

Triglycerides feed the Friedewald equation that most laboratories use to calculate LDL-C from total cholesterol. When triglycerides are high the calculated LDL-C becomes unreliable, and the total remains the one directly measured value on the panel.

Apolipoprotein B same panel

ApoB counts atherogenic particles directly, whereas total cholesterol counts cholesterol mass across all of them. When the two disagree — common with high triglycerides, diabetes or obesity — apoB is the better guide to risk.

Thyroid Stimulating Hormone can distort it

An underactive thyroid raises total cholesterol and an overactive one lowers it. Thyroid function is usually checked before a newly found high value is treated as a lipid problem.

Which foods affect TC?

• Replacing saturated fat with unsaturated fat — olive or rapeseed oil, nuts and oily fish in place of butter, fatty meat and palm oil — lowers strong evidence
• Soluble fibre — oat and barley beta-glucan, legumes, psyllium — lowers strong evidence
• Foods fortified with plant sterols or stanols — lowers strong evidence
• Industrial trans fats from partially hydrogenated oils — raises strong evidence
• Unfiltered coffee — French press, boiled, Turkish — whose cafestol raises cholesterol; paper-filtered coffee does not — raises moderate evidence

Which supplements are studied for TC?

Plant sterols / stanols strong evidence

Plant sterols displace cholesterol from the mixed micelles that carry it across the intestinal wall, so less is absorbed. About 2 g a day lowers LDL-C, and therefore total cholesterol, by roughly 8-10%, and the effect is additive to statins.
Typical dose: 2 g/day, taken with meals
Cautions: Not suitable in sitosterolaemia, a rare inherited disorder in which plant sterols are absorbed excessively. Slightly reduces absorption of carotenoids; a diet rich in vegetables offsets this.

Oat beta-glucan moderate evidence

A viscous soluble fibre that binds bile acids in the gut and thickens intestinal contents, so the liver draws on circulating cholesterol to make replacement bile. Around 3 g a day lowers total and LDL cholesterol by roughly 5%.
Typical dose: 3 g/day, from oats or as a supplement
Cautions: Bloating and wind are common when the dose is increased quickly; build up over one to two weeks. Take other medicines at least two hours apart, since viscous fibre can slow their absorption.

Red yeast rice moderate evidence

Red yeast rice contains monacolin K, which is chemically identical to the statin lovastatin, and lowers cholesterol by the same enzyme inhibition a statin uses.
Typical dose: no general dose given
Cautions: This is a statin sold as a supplement: the same muscle and liver-enzyme risks apply, without a prescriber watching for them. Monacolin content varies widely between products and batches, so the actual dose taken is unknown. Not to be combined with a prescribed statin, and not for use in pregnancy or breastfeeding. A doctor should know before it is started.

How does exercise affect TC?

Regular aerobic exercise moderate evidence

How much: At least 150 minutes a week at moderate intensity, or 75 minutes vigorous, spread across most days.
What to expect: Aerobic exercise lowers total cholesterol only slightly — a few percent — because its main lipid effects are on triglycerides and HDL-C rather than on LDL. Its value for cardiovascular risk is large despite the small change in this number.

Resistance training moderate evidence

How much: Two or three sessions a week covering the major muscle groups.
What to expect: Resistance training produces a small reduction in total and LDL cholesterol in meta-analyses, and it preserves muscle during weight loss — the period in which lipid improvements are largest.

Which lifestyle factors affect TC?

Body weight strong evidence

Weight loss lowers total cholesterol modestly — on the order of 0.05 mmol/L per kilogram lost in pooled trials — with larger gains in triglycerides and HDL-C. The effect on the total is real but small, so it is not the number by which a weight-loss effort is best judged.

Smoking strong evidence

Smoking barely changes total cholesterol yet multiplies the harm the cholesterol does, by oxidising LDL and injuring the artery lining. For cardiovascular risk, stopping smoking outweighs almost any adjustment that could be made to this number.

Reading the total in context strong evidence

Total cholesterol is one input to a risk estimate that also depends on age, sex, blood pressure, smoking and diabetes. The same value can mean very different things for a 30-year-old non-smoker and a 60-year-old with hypertension, which is why guidelines score overall risk rather than react to the cholesterol number alone.

How should you prepare for a TC test?

• Fasting is not required for routine screening; the total changes little after a meal. Fast if triglycerides are known to be high or a calculated LDL-C is needed.
• Sit for several minutes before the draw and ask that the tourniquet be released promptly; posture and venous stasis can shift the result by 5-10%.
• Avoid testing during or in the weeks after an infection, operation or heart attack, when the value reads falsely low.
• Ask for the full panel, not the total alone. LDL-C, HDL-C and triglycerides — or apoB — are what turn the total into something interpretable.
• Track change using the same laboratory and method. Between-laboratory differences can be as large as the change being looked for.

References

1. Mach F et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias. Eur Heart J 2020 — https://doi.org/10.1093/eurheartj/ehz455
2. Grundy SM et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol. Circulation 2019 — https://doi.org/10.1161/CIR.0000000000000625
3. Prospective Studies Collaboration (Lewington S et al.). Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta-analysis of individual data from 61 prospective studies. Lancet 2007 — https://doi.org/10.1016/S0140-6736(07)61778-4
4. Nordestgaard BG et al. Fasting is not routinely required for determination of a lipid profile — joint consensus statement from the EAS and EFLM. Eur Heart J 2016 — https://doi.org/10.1093/eurheartj/ehw152