Updated: 2026-08-31

This article takes five indicators (selected for ease of comparison, not any ranking) — ⚠️ two of which, blood pressure and BMI, are not blood tests but measurements. Their "thresholds" are not the same kind of thing. Cholesterol — the Centre for Health Protection's Cholesterol leaflet (2025 revision) gives total cholesterol "below 5.2", LDL "below 3.4 (below 2.6 is more desirable)" and HDL "above 1.0 (1.6 or above is more desirable)", but the same leaflet calls these "statistically derived desirable levels, for reference" — not diagnostic thresholds — and there is no triglycerides row; ⚠️ the "desirable levels" table is not broken down by sex, but that does not mean no HDL classification is: the CHP's Population Health Survey defines "low" HDL as below 1.3 mmol/L for women and below 1.0 for men. Blood pressure — 140/90, 135/85 and 130/80 are not three degrees of severity: Hong Kong's hypertension reference framework states that ≥130/80 over 24 hours, ≥135/85 daytime and ≥120/70 night-time are "all equivalent to office BP ≥ 140/90 mmHg" — one threshold, written three ways for three measurement settings. glycated haemoglobin — WHO's 2011 recommendation gives 6.5% as the diagnostic cut point, but the same passage states "A value of less than 6.5% does not exclude diabetes diagnosed using glucose tests", and the recommendation's GRADE strength is only conditional. ⚠️ More important still: an asymptomatic person cannot be diagnosed on one result — the Population Health Survey states "for an asymptomatic patient, an additional HbA1c or blood glucose result is needed to diagnose diabetes". BMI — two documents from the same body: one gives 18.5 to 22.9 as the "normal" range for Asian adults, the other uses 23.0/25.0 as the overweight/obesity cut-offs: the two numbers are doing two different jobs. ALT — none of the sources opened for this article prints a Hong Kong official upper limit for ALT; the interval printed on the right of your report is adopted and validated by the laboratory that issued it (which may have established it itself, adopted a manufacturer's or the literature's interval and validated it, or transferred an existing one). This article sets out the figures and wording each official document prints. It does not judge your number and offers no medical advice.

First, a distinction: there are four kinds of "threshold"

Behind the numbers on a single report can sit four completely different kinds of line.

  • A diagnostic threshold — defining whether a disease is present (glycated haemoglobin 6.5%, for example).
  • A desirable level — a statistically "better" position, which does not mean that below it you are fine and above it you are ill (cholesterol, for example).
  • A treatment target — what to control to after diagnosis, and it varies with the condition: Hong Kong's hypertension reference framework gives <140/90 as the initial goal for uncomplicated hypertension, 130/80 or lower for those who can tolerate it, and separate targets for patients with diabetes or chronic kidney disease.
  • A laboratory reference interval — the range printed on the right of the report, adopted and validated by the laboratory that issued the report. ⚠️ It is not necessarily one they produced themselves: the laboratory may establish it, adopt a manufacturer's or the literature's interval and validate it, or transfer an existing interval mathematically.

Confusing these four kinds of line can lead to misunderstanding. For each indicator below, the article says which kind it is.

One. Cholesterol: three rows of numbers, and one qualifying sentence

The table from the Centre for Health Protection's Cholesterol leaflet (the leaflet prints "2025 revision"), reproduced with the sentence that introduces it.

"cholesterol levels can be determined by a blood test, to help assess the risk of coronary heart disease. The following are the statistically derived desirable levels of cholesterol, for reference."

Desirable cholesterol levels (mmol/L). Source: Department of Health, Centre for Health Protection, *Cholesterol* leaflet, the leaflet prints "2025 revision", retrieved 2026-08-30. ⚠ The leaflet describes these as "statistically derived" "desirable levels", "for reference" — not diagnostic thresholds.
CategoryDesirable level
Total cholesterolbelow 5.2
LDL cholesterol
(commonly "bad cholesterol")		below 3.4
(below 2.6 is more desirable)
HDL cholesterol
(commonly "good cholesterol")		above 1.0
(1.6 or above is more desirable)

⚠️ Three things to note, all of them things the table does not have:

  1. There is no triglycerides (TG) row. The table has three rows only.
  2. HDL is not split by sex in this table — but you cannot infer from that that no classification splits by sex. This table prints "desirable levels", not broken down by sex. ⚠️ The same body (the Centre for Health Protection), in its Population Health Survey 2020-22, defines low HDL cholesterol as below 1.3 mmol/L for women and below 1.0 mmol/L for men, and separately sets "desirable" at above 1.5 for both sexes. In other words: one indicator, different thresholds for different purposes, and one of them does split by sex.
  3. The bracketed figure is "more desirable", not a second threshold. "Below 2.6 is more desirable" and "below 3.4" are two levels on the same row, not a grading in which below 3.4 passes and below 2.6 is excellent.

The leaflet also states what the numbers are for: "to help assess the risk of coronary heart disease" — a reference for risk assessment, not a diagnosis.

Two. Blood pressure: 140/90, 135/85 and 130/80 are not three degrees of severity

They are one threshold, written for three measurement settings.

Hong Kong's Reference Framework for Hypertension Care for Adults in Primary Care Settings (cover prints Revised Edition 2021; first published 2010; last review 2021) — quoted from the English original:

"The values are, on average, lower than office BP values, and the diagnostic threshold for hypertension is ≥ 130/80 mmHg over 24 h, ≥ 135/85 mmHg for the daytime average, and ≥ 120/70 for the night time average (all equivalent to office BP ≥ 140/90 mmHg)."

(In plain terms: a 24-hour average of ≥130/80, a daytime average of ≥135/85 and a night-time average of ≥120/70 are the diagnostic thresholds — all equivalent to a clinic BP of ≥140/90.)

And for home measurement, the same document:

"Persons with an average BP 135/85 mmHg measured at home are generally considered to be hypertensive."

(In plain terms: an average home blood pressure of 135/85 is generally regarded as hypertension.)

Diagnostic thresholds for hypertension, by measurement setting. Source: Hong Kong Reference Framework for Hypertension Care for Adults in Primary Care Settings (cover prints Revised Edition 2021), retrieved 2026-08-30. ⚠ The same document states that each is "equivalent to" office BP ≥140/90.
SettingDiagnostic threshold
Clinic (office)≥ 140/90
Home measurement (average)135/85
24-hour ambulatory monitoring (24-hour average)≥ 130/80
24-hour ambulatory monitoring (daytime average)≥ 135/85
24-hour ambulatory monitoring (night-time average)≥ 120/70

⚠️ The practical consequence: measuring your reading at home against the clinic's 140/90 is measuring against the wrong ruler. The home threshold is 135/85, lower than the clinic's.

⚠️ And there is a further layer: 135/85 is an average, not a single reading. The framework sets out the home method — two consecutive measurements at least 1 to 2 minutes apart, seated, recorded twice daily, morning and evening; initial assessment or assessment of treatment effect should cover seven days, and then "The average of the readings is taken as the home BP level". A single reading is not the number it is talking about.

A different set of numbers must not be confused with the above — treatment targets. From the same document:

"The initial goal of therapy for uncomplicated hypertensive patients is blood pressure below 140/90mmHg; and for individuals who can tolerate, the blood pressure should be targeted to 130/80mmHg or lower." "8.3.2 Patient with hypertension and diabetes — Target blood pressure is below 130/80 mmHg."

⚠️ A diagnostic threshold and a treatment target are two different things: the first answers "do I have hypertension"; the second answers "once on treatment, what should it be controlled to". The <130/80 for patients with diabetes is a target, not a statement that their diagnostic threshold is lower.

Three. glycated haemoglobin: 6.5% comes with five qualifications

The World Health Organization's 2011 recommendation, quoted in full from the English original — because every sentence narrows the conclusion.

"HbA1c can be used as a diagnostic test for diabetes providing that stringent quality assurance tests are in place and assays are standardised to criteria aligned to the international reference values, and there are no conditions present which preclude its accurate measurement.

An HbA1c of 6.5% is recommended as the cut point for diagnosing diabetes. A value of less than 6.5% does not exclude diabetes diagnosed using glucose tests.

Quality of evidence assessed by GRADE: moderate Strength of recommendation based on GRADE criteria: conditional"

(In plain terms: HbA1c can serve as a diagnostic test for diabetes provided strict quality assurance is in place and assays are standardised; 6.5% is the recommended cut point, and a value below 6.5% does not exclude diabetes diagnosed by glucose testing.)

The same report is explicit about something it does not say:

"The expert group concluded that there is currently insufficient evidence to make any formal recommendation on the interpretation of HbA1c levels below 6.5%."

(In plain terms: the expert group found the evidence insufficient for any formal recommendation on interpreting levels below 6.5%.)

And a very direct caution:

"many people identified as having diabetes based on HbA1c will not have diabetes by direct glucose measurement"

⚠️ Two points that must be spelled out:

  • The threshold originates in WHO's recommendation, but local official documents print it too. The CHP's Population Health Survey 2020-22 states "WHO recommends an HbA1c of 6.5% or above as the cut point for diagnosing diabetes" and uses 「糖化血紅素 ≥ 6.5%」 in its survey classification; the Hong Kong Reference Framework for Diabetes Care for Adults in Primary Care Settings (Revised Edition 2023) prints the same threshold (Table 4: HbA1c ≥6.5%).
  • ⚠️ For an asymptomatic person, one result is not enough. The Population Health Survey states 「對於無症狀的患者，需要額外的糖化血紅素或血糖測試結果來診斷糖尿病」; the diabetes reference framework puts it plainly, in the English original: "The diagnosis of diabetes in an asymptomatic person should not be made on the basis of a single abnormal plasma glucose or HbA1c value. At least one additional HbA1c or plasma glucose test result with a value in the diabetic range is required."
  • "A value of less than 6.5% does not exclude diabetes" is in the original text — so a result of 6.2% is not a conclusion that you have passed.

Four. BMI: one body, two documents, two numbers

Both are right, because they are doing two different jobs.

  • The Centre for Health Protection's Cholesterol leaflet (2025 revision): "the normal BMI for Asian adults is 18.5 to 22.9", noting that "the above is issued by the WHO Regional Office for the Western Pacific for Asian adults, and does not apply to children under 18 or to pregnant women".
  • Population Health Survey 2020-22 (Part II): using the same WHO Western Pacific classification for Asian adults, overweight is 23.0 ≤ BMI < 25.0 and obesity is BMI ≥ 25.0.

⚠️ 18.5–22.9 is a "normal" range; 23.0/25.0 are overweight/obesity cut-offs. There is no contradiction in the gap between them (22.9 to 23.0); the two documents are saying different things — one a desirable range, the other classification cut-offs.

And one thing that is easily got wrong: which classification you use changes the answer a lot. The same survey report states that under the Asian adult classification, the age-standardised prevalence of overweight and obesity among people aged 18–84 was 51.3%; under the WHO general classification (overweight ≥25.0, obesity ≥30.0), the same population gives 30.8%. So "is my BMI normal" has to begin with "under which classification".

Five. ALT (alanine aminotransferase): the row with no threshold

None of the sources opened for this article prints a Hong Kong official upper limit for ALT.

⚠️ This article cites no ALT threshold figure, for this reason: among all the documents opened for it on 30 August 2026 — the CHP cholesterol leaflet, the Population Health Survey report, the hypertension reference framework, WHO's glycated haemoglobin report, the Hong Kong Medical Journal reference-interval survey and the Australian Prescriber article — not one prints an upper limit for ALT adopted officially in Hong Kong.

So who sets the limit printed on the right of your report? The laboratory that issued it, which adopts and is responsible for validating it — it may have established the interval itself, adopted a manufacturer's or the literature's interval and validated it, or transferred an existing interval. This has been measured locally: a 2019 Hong Kong Medical Journal survey, covering analytes including alanine aminotransferase (ALT), found differences between laboratories in the upper limits of reference intervals — in the original, "inter-laboratory percentage differences of upper RI limits were up to 47%", and that 47% (an absolute difference of 16 U/L) was for aspartate aminotransferase (AST).

⚠️ To be precise: 47% is the maximum across analytes, and it is the AST figure, not the ALT figure. This article does not transfer it to ALT.

The practical conclusion: read the range printed on your own report, and do not measure it against the range on a different report. This site has a separate article on exactly that; see the links at the end.

The same Australian Prescriber article also cautions that liver enzymes should be read together: "When deciding if a result is abnormal, look at related tests. Alkaline phosphatase is one of the 'liver function tests' (others are bilirubin, gamma glutamyl transferase, alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase)."

Why does testing more things make at least one out-of-range result more likely?

Because a reference range, by definition, leaves out a proportion of healthy people.

The worked illustration in Australian Prescriber (2009), from the English original:

"Assuming these results were all independent of each other (which they are not) and that results from the reference population are normally distributed (which they may not be), only 36% of normal people will have all 20 results in the reference range. There will be 64% with at least one abnormal result"

⚠️ The two parenthetical caveats are the author's own: they immediately note that the assumption of independence does not hold, and that normal distribution may not hold either. So the 36% is an illustrative calculation, not a measured proportion. The point being made is: the more items you test, the greater the chance that at least one falls outside range.

Ask about these

Five questions before you take the report to a doctor:

  1. Is this threshold a diagnosis, a desirable level, a treatment target, or the laboratory's reference interval? Four different things, four different meanings.
  2. The three cholesterol figures are "desirable levels" — do I need to act on them? The Centre for Health Protection itself calls them "statistically derived" and "for reference", used to assess coronary heart disease risk.
  3. Did I measure my blood pressure at the clinic or at home, and how many times? The clinic uses 140/90 and home uses 135/85 — and the home figure is an average over morning and evening readings across seven days, not a single reading.
  4. Does an HbA1c result above or below 6.5% settle it? Neither can be concluded from one result: WHO's original states that a value below 6.5% does not exclude diabetes diagnosed using glucose tests, and an asymptomatic person above the threshold needs an additional result before a diagnosis.
  5. Which laboratory set the ALT upper limit on my report? Reference intervals differ between laboratories; read the range on your own report.

What to do about it is for a doctor to decide — this article explains what the numbers are, and does not judge what yours means.

Frequently asked questions

  • Total cholesterol of 5.4 — is that high cholesterol? This article makes no judgement. The Centre for Health Protection's Cholesterol leaflet (2025 revision) gives a "desirable level" of below 5.2 for total cholesterol, and states that these are "statistically derived" "desirable levels", "for reference", used to help assess the risk of coronary heart disease — not diagnostic thresholds. What it means for you is for a doctor to judge on your overall condition.
  • Why is there no triglycerides row on the leaflet? The leaflet's table has three rows only: total cholesterol, LDL cholesterol and HDL cholesterol. This article cites no official threshold for triglycerides.
  • Is the good-cholesterol threshold different for men and women? It depends on the purpose. The Centre for Health Protection's Cholesterol leaflet does not break its "desirable levels" table down by sex, giving only "above 1.0 (1.6 or above is more desirable)"; but the same body's Population Health Survey 2020-22, in defining low HDL cholesterol, uses below 1.3 mmol/L for women and below 1.0 mmol/L for men, and sets "desirable" at above 1.5 mmol/L for both sexes. That the leaflet does not split by sex does not mean no HDL classification does.
  • How do I read a home blood pressure monitor against the threshold? This article makes no diagnosis. Hong Kong's hypertension reference framework states that a person with an average home BP of 135/85 is generally considered hypertensive, and that this value is the same threshold as the clinic's ≥140/90 expressed for a different measurement setting. The framework's home method is: two consecutive measurements at least 1 to 2 minutes apart, seated, recorded morning and evening, with initial assessment covering seven days, taking the average of the readings as the home BP level. A single reading is not the value the threshold refers to; the actual judgement must be made by a doctor.
  • Are 140/90, 135/85 and 130/80 three degrees of severity? No. The framework states that a 24-hour average of ≥130/80, a daytime average of ≥135/85 and a night-time average of ≥120/70 are all "equivalent to" an office BP of ≥140/90. Separately, <140/90 and <130/80 are treatment targets in the same document, which is a different thing from a diagnostic threshold.
  • Who set glycated haemoglobin 6.5%, and on what conditions? The World Health Organization's 2011 report recommends 6.5% as the cut point for diagnosing diabetes, and Hong Kong's diabetes reference framework (Revised Edition 2023) and the Centre for Health Protection's Population Health Survey print the same value. The framework also states that a diagnosis of diabetes in an asymptomatic person should not be made on a single abnormal plasma glucose or glycated haemoglobin value, and that at least one additional result in the diabetic range is required. WHO's conditions are that stringent quality assurance is in place, that assays are standardised to the international reference values, and that no conditions are present which preclude accurate measurement. The recommendation's GRADE quality of evidence is moderate and its strength is conditional. The same report states that a value below 6.5% does not exclude diabetes diagnosed using glucose tests, and that the expert group considered there was insufficient evidence to make any formal recommendation on interpreting levels below 6.5%.
  • Which is right, BMI 18.5–22.9 or 23/25? Both are WHO Western Pacific indicators for Asian adults, doing different jobs: the Centre for Health Protection's Cholesterol leaflet gives 18.5 to 22.9 as the normal BMI for Asian adults; the Population Health Survey report uses 23.0 ≤ BMI < 25.0 for overweight and BMI ≥ 25.0 for obesity.
  • Does Hong Kong have an official ALT upper limit? Among all the sources opened for this article on 30 August 2026, none prints an upper limit for ALT adopted officially in Hong Kong. The reference interval on a report is adopted and validated by the laboratory that issued it — it may be established by that laboratory, adopted from a manufacturer or the literature and validated, or transferred from an existing interval. A 2019 Hong Kong Medical Journal survey (covering analytes including ALT) found differences between laboratories in the upper limits of reference intervals; its maximum difference of 47% (an absolute difference of 16 U/L) was for AST.

Also in this series:

  • Why the ruler on the right of the report differs: “How should laboratory and imaging reports be read? The 'normal range' is a property of the laboratory, not of your body”
  • Whether to treat high cholesterol, and what the evidence says: “How is the 51.9% for high cholesterol calculated? A full breakdown of whether Hong Kong has its own LDL target, and the randomised data on statin muscle pain 2026”
  • What to do after a report says "abnormal": “Your check-up report says 'abnormal' — what next? Two centres, two answers for one person; what the official position is, and how a public referral works”

What this article does not claim

  • It judges no reader's test result and recommends no treatment or medication. Every threshold is quoted, with its source, its nature (diagnostic / desirable level / treatment target) and the date the document itself prints.
  • It cites no official threshold for triglycerides. The table in the Centre for Health Protection's Cholesterol leaflet has no such row.
  • It cites no ALT threshold figure. None of the sources opened prints an upper limit for ALT adopted officially in Hong Kong; the several upper limits circulating informally are not used here.
  • It does not apply the Hong Kong Medical Journal's 47% to ALT. That figure is the maximum across analytes and is reported for AST, an absolute difference of 16 U/L.
  • It does not treat WHO's HbA1c recommendation as a definition set by the Hong Kong Department of Health. The 6.5% threshold originates in WHO's recommendation; the Centre for Health Protection's Population Health Survey and the Hong Kong Reference Framework for Diabetes Care both print and use the same value, as the article states in the body. That recommendation was made by the World Health Organization in 2011. The distinction drawn here is about the origin of the threshold, not about whether local documents print it.
  • It provides no thresholds for tests outside these five categories. Other test names appear only in the liver function panel and in the 20-test worked illustration, with no numerical threshold given for them. "Five" is a selection made for readability, not any body's ranking of the most common; none of the sources opened ranks tests by frequency or describes how check-up packages are composed. Blood pressure and BMI are measurements rather than blood tests, as the article notes.
  • It does not claim that misreading thresholds is the main cause of false alarms. None of the sources opened provides such a statistic.
  • It does not cite the Centre for Health Protection's BMI chart leaflet or its "are you overweight" leaflet. Both pages showed only an image container with no readable text when opened on 30 August 2026; the BMI figures are taken instead from the Cholesterol leaflet and the Population Health Survey report.
  • The Australian Prescriber 36% is a worked illustration, not a measured proportion. The author states that it rests on two assumptions they consider not to hold, and the article quotes that alongside.
  • The hypertension reference framework, the WHO report, the Hong Kong Medical Journal paper and Australian Prescriber are English-language sources. This English version quotes them from their English originals.

Provenance: compiled from official leaflets, official survey reports, reference frameworks and international organisation documents; every threshold is marked with its source, its nature and the date the document itself prints.

Quotations from Chinese-language official documents and press materials appear in our own English translation; the original wording governs.

資料來源 (Sources)

Compiled by the editorial team from official documents and academic literature; every threshold is attributed to its source. This is health information, not medical advice.