# Lipid Profile Interpretation

> Lipid profile interpretation in MBBS Biochemistry: LDL, non-HDL cholesterol, Friedewald formula, dyslipidaemia patterns and Indian risk targets.

- Canonical URL: https://prepelephant.com/topics/mbbs/biochemistry/lipid-profile-interpretation-biochem
- Exam / course: MBBS · Subject: Biochemistry
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Lipid Profile Interpretation", PrepElephant, https://prepelephant.com/topics/mbbs/biochemistry/lipid-profile-interpretation-biochem

## Direct answer

A standard lipid panel reports total cholesterol, HDL cholesterol, triglycerides and a calculated LDL cholesterol, most often by the Friedewald equation — LDL equals total cholesterol minus HDL minus triglycerides divided by five in mg/dL — an estimate that fails when triglycerides exceed 400 mg/dL, in which case direct LDL or non-HDL must carry the interpretation. Non-HDL cholesterol (total minus HDL), representing all atherogenic particles, is valid fasting or fed, and its goal is simply the LDL goal plus 30 mg/dL. Indian lipid profiles skew toward high triglycerides and low HDL (atherogenic dyslipidaemia of the metabolic syndrome), so the LDL-centric report hides risk that non-HDL and apolipoprotein B expose.

## What you must remember

- **Desirable ranges (adults, mg/dL):** total cholesterol below 200, LDL below 100 (below 70 in established coronary disease or diabetes), HDL above 40 in men and 50 in women, triglycerides below 150; triglycerides of 500 or more signal pancreatitis risk and shift priority to fibrates first.
- **Friedewald formula:** LDL = TC − HDL − TG/5; invalid when TG > 400 mg/dL, in type III hyperlipoproteinaemia, or on non-fasting samples with high TG — use direct LDL-C or the non-HDL value instead.
- **Non-HDL cholesterol** = TC − HDL; goal = LDL goal + 30 mg/dL (e.g. < 100 mg/dL when the LDL goal is 70); it captures VLDL, IDL and Lp(a) cholesterol as well.
- **Secondary causes to exclude before labelling any dyslipidaemia primary:** hypothyroidism (check TSH — the commonest reversible cause in Indian clinics), diabetes, nephrotic syndrome, chronic kidney disease, obstructive liver disease, alcohol, thiazides, beta blockers, steroids, antiretrovirals.
- **Indian phenotype:** the atherogenic triad of high triglycerides, low HDL and small dense LDL predominates; LDL may look deceptively modest while non-HDL and apo B are high — a reason guidelines for South Asians recommend treating at lower LDL thresholds.
- **Sample conditions:** a 9-12 hour fast was traditional; non-fasting sampling is now acceptable for most purposes except known hypertriglyceridaemia, where fasting values guide fibrate therapy.
- **Remnant cholesterol** (approximately non-HDL minus LDL) is emerging as an inflammatory, atherogenic fraction — worth one line in a good answer.

## Reading one report line by line

Consider a 45-year-old Sikh businessman with a family history of early MI: TC 232, HDL 34, TG 320 mg/dL. Friedewald gives LDL = 232 − 34 − 64 = 134 mg/dL, apparently only borderline. But two corrections follow. First, with TG at 320, the formula's TG/5 term is least reliable, so cross-check with non-HDL = 232 − 34 = 198 mg/dL — nearly double any reasonable goal of 100 for a high-risk South Asian. Second, request apo B: at this triglyceride level, particle number is likely high from small dense LDL and remnants. Now the plan becomes biochemically honest: rule out secondary causes with TSH, HbA1c, creatinine, urine protein; treat with a moderate- or high-intensity statin plus attention to refined carbohydrate and alcohol (both raise TG in Indians disproportionately); add fenofibrate only if TG stays above about 500 mg/dL for pancreatitis prevention, since fibrate-outcome data in combination therapy are neutral outside severe hypertriglyceridaemia. The teaching point is procedural: never read the LDL line alone — read the triglyceride line first, because it decides whether the LDL line can be trusted.

## How the examiner frames it

Three recurring demands. One: "Why is non-HDL better than LDL in this report?" — because it includes every apo B particle's cholesterol and survives high TG. Two: "Patient non-fasting, does it invalidate?" — no for TC, HDL, non-HDL; TG rises modestly after food, so recheck fasting if TG is elevated. Three: the numerical trap of the Friedewald formula in SI units — divide triglycerides by 2.2, not 5, when everything is in mmol/L; Indian laboratories report both units, and candidates routinely mix them.

## Frequently asked questions

### When does the Friedewald formula fail?

When triglycerides exceed 400 mg/dL, in type III dysbetalipoproteinaemia, and with markedly non-fasting samples; use direct LDL or non-HDL instead.

### How is non-HDL cholesterol calculated and what is its goal?

Total cholesterol minus HDL cholesterol, with a target of LDL goal plus 30 mg/dL; it needs no fasting sample.

### Which secondary cause of dyslipidaemia must be excluded first?

Hypothyroidism, by a TSH assay, since it elevates LDL through reduced receptor clearance and is fully reversible with levothyroxine.

### Why do Indian lipid profiles need tighter interpretation?

South Asian dyslipidaemia features high triglycerides, low HDL and small dense LDL, so risk persists at modest LDL levels and non-HDL or apo B uncovers it.

### What triglyceride level changes management priority?

Above about 500 mg/dL, pancreatitis risk dominates and triglyceride lowering (fibrate, omega-3 fatty acids, strict diet, alcohol cessation) takes precedence over LDL.