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LDL Cholesterol Calculator

Q: Why is Friedewald invalid at high triglycerides?

The TG/5 term assumes a fixed VLDL composition; above 400 mg/dL (and in chylomicronaemia) it overestimates VLDL and underestimates LDL, so the calculator returns an error instead of a number.

Q: What is non-HDL cholesterol for?

It captures all atherogenic lipoproteins (LDL, VLDL, IDL, Lp(a)) and stays valid in non-fasting samples; targets are usually 30 mg/dL (0.8 mmol/L) above the LDL target.

Calculates LDL cholesterol from total cholesterol, HDL and triglycerides with the Friedewald equation (mg/dL or mmol/L), plus non-HDL cholesterol and the NCEP LDL category.

When to use

You have a fasting lipid panel without a direct LDL measurement and need the calculated LDL or non-HDL cholesterol.

Do not use when: Triglycerides exceed 400 mg/dL (4.5 mmol/L) or the sample was non-fasting; Friedewald is invalid there and a direct LDL assay or the Martin/Hopkins or Sampson equations are used instead.

Formula

LDL = total_cholesterol − hdl_cholesterol − triglycerides / 5 (mg/dL) or − triglycerides / 2.2 (mmol/L); non-HDL = total_cholesterol − hdl_cholesterol

Friedewald (1972) assumes VLDL cholesterol ≈ TG/5 in fasting samples; accuracy falls when TG is 200–400 mg/dL or LDL is below 70 mg/dL. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Required	Description
`total_cholesterol`	number	yes	Total cholesterol in the chosen unit. Range: > 0, ≤ 2000
`hdl_cholesterol`	number	yes	HDL cholesterol in the chosen unit. Range: > 0, ≤ 500
`triglycerides`	number	yes	Fasting triglycerides in the chosen unit. Range: > 0, ≤ 5000
`unit`	enum: mg_dl \| mmol_l	default mg_dl	Unit shared by all three inputs.

Outputs

Output	Type	Unit	Description
`ldl_cholesterol`	number		Calculated LDL in the input unit.
`non_hdl_cholesterol`	number		Total − HDL, in the input unit.
`unit`	string		Unit of the two values above.
`ldl_cholesterol_mg_dl`	number	mg/dL	LDL in mg/dL.
`ldl_cholesterol_mmol_l`	number	mmol/L	LDL in mmol/L (mg/dL × 0.02586).
`ldl_category`	string		Optimal <100, near optimal 100–129, borderline high 130–159, high 160–189, very high ≥190 mg/dL.

Example

TC 200, HDL 50, TG 150 mg/dL: {"total_cholesterol":200,"hdl_cholesterol":50,"triglycerides":150,"unit":"mg_dl"} → {"ldl_cholesterol":120,"non_hdl_cholesterol":150,"ldl_cholesterol_mmol_l":3.1,"ldl_category":"Near optimal (100–129 mg/dL)"}

TC 5.2, HDL 1.3, TG 1.5 mmol/L: {"total_cholesterol":5.2,"hdl_cholesterol":1.3,"triglycerides":1.5,"unit":"mmol_l"} → {"ldl_cholesterol":3.22,"non_hdl_cholesterol":3.9,"ldl_cholesterol_mg_dl":124.4}

GET https://tttkmbb.com/api/v1/calculate/ldl-cholesterol?total_cholesterol=200&hdl_cholesterol=50&triglycerides=150&unit=mg_dl

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/ldl-cholesterol (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/ldl-cholesterol · Markdown: https://tttkmbb.com/medical/ldl-cholesterol.md · JSON definition: https://tttkmbb.com/medical/ldl-cholesterol.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="ldl-cholesterol"
OpenAPI operationId: calculate_ldl_cholesterol
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Why is Friedewald invalid at high triglycerides?

The TG/5 term assumes a fixed VLDL composition; above 400 mg/dL (and in chylomicronaemia) it overestimates VLDL and underestimates LDL, so the calculator returns an error instead of a number.

What is non-HDL cholesterol for?

It captures all atherogenic lipoproteins (LDL, VLDL, IDL, Lp(a)) and stays valid in non-fasting samples; targets are usually 30 mg/dL (0.8 mmol/L) above the LDL target.

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