Methodology
Every result you get from us carries two things. The first is the laboratory reference range, and that one is never ours: it is always the interval your laboratory reported for that marker, for your sex. We store it exactly as it arrives and we never substitute a number of our own for it.
The second is the range we look for. That one is ours, it is narrower than the laboratory's, and every one of them is on this page with the document it came from. Where a marker has no agreed range beyond the laboratory's, this page says so and your result says so too. That is more of the table than you might expect, and printing it is the point.
Ranges differ by sex, and for a few markers by age or by the time of day the sample was taken, so this page lists each version separately. We never apply a range for one sex to the other, and where we do not hold your sex at birth we show the laboratory's range alone rather than guessing.
One blood test is a snapshot of one day. None of this is a diagnosis and none of it replaces a conversation with your GP.
40 markers · Range table version 2026-09-08.1
The main protein your liver makes to hold fluid inside blood vessels and carry hormones and minerals around.
Sold as Albumin
No agreed tighter range
There is no agreed research range for albumin beyond the laboratory's. It falls with inflammation and rises with dehydration, so a high-normal figure would reward a dry sample.
An enzyme found mainly in liver and bone, which is why it moves for reasons in either.
Sold as ALP
No agreed tighter range
There is no agreed research range for alkaline phosphatase beyond the laboratory's. It mixes liver and bone forms, and it rises after the menopause and in pregnancy.
An enzyme that lives inside liver cells and leaks into the blood when they are under strain.
Sold as Liver function (ALT)
male
We look for at or below 33 U/L.
Clinical guideline. A named clinical guideline sets this number.
ACG 2017 abnormal liver chemistries guideline, with Prati 2002
The ACG healthy-population figure for men is 29 to 33 U/L. Many UK laboratories report a wider interval, so this often sits inside the laboratory's own range.
female
We look for at or below 25 U/L.
Clinical guideline. A named clinical guideline sets this number.
ACG 2017 abnormal liver chemistries guideline, with Prati 2002
The ACG healthy-population figure for women is 19 to 25 U/L, materially lower than the male one and than most laboratory intervals.
A direct count of the particles capable of entering an artery wall, one tag per particle.
Sold as ApoB
adults
We look for at or below 1 g/L.
Clinical guideline. A named clinical guideline sets this number.
ESC/EAS 2019 dyslipidaemia guideline, moderate-risk goal
1.00 g/L is 100 mg/dL. The laboratory reference interval is sex-split; this guideline figure is not. Tighter goals of 0.80 and 0.65 need an assessed risk category, which a blood test alone cannot give you.
A protein the liver releases when something is inflamed, measured on the standard assay that reports down to about 5 mg/L.
Sold as C-Reactive Protein (CRP)
No agreed tighter range
A standard-sensitivity CRP cannot resolve the low bands the research uses, so there is no agreed research range to show beside it. The high-sensitivity version of the same test can.
The balance between your total cholesterol and the protective fraction, shown for context.
Sold as Cholesterol:HDL ratio, Total:HDL ratio
adults
Convention puts this at at or below 4 ratio, which is not a guideline, so it is never drawn beside your result.
Convention. A convention rather than evidence, so we say the numbers in words and never draw them as a band.
HEART UK convention; the ratio is the lipid input to QRISK3
A convention rather than a guideline figure, and it improves with a rise in HDL that carries no proven benefit. Stated in prose, never drawn as a band.
The adrenal hormone that follows a daily rhythm, highest shortly after waking and lowest late at night.
Sold as Cortisol
No agreed tighter range
There is no agreed research range for cortisol beyond the laboratory's. The NICE thresholds are assay specific and apply to a timed 07:00 to 10:00 sample, and a high reading inside the laboratory's range is not a measure of stress.
A waste product your muscles make at a steady rate, which your kidneys clear, so it reflects both muscle mass and filtration.
Sold as Creatinine
No agreed tighter range
There is no agreed research range for creatinine beyond the laboratory's, and the laboratory's is sex-split because it reflects muscle mass as much as filtration. The interpretable number is eGFR.
An adrenal hormone the body uses as raw material for other sex hormones. It peaks in your twenties and falls steadily with age.
Sold as DHEA-S
No agreed tighter range
There is no agreed research range for DHEA sulphate beyond the laboratory's, which is already banded by age and sex. Its association with mortality is J-shaped, so neither higher nor lower is better.
An estimate of how much blood your kidneys filter each minute, calculated from creatinine with your age and sex.
Sold as eGFR
adults
We look for at or above 90 mL/min/1.73m2.
Clinical guideline. A named clinical guideline sets this number.
KDIGO 2024 CKD guideline, category G1
The equation already applies your age and sex, so no further age band is added here. UK laboratories are not standardised on one equation.
How much iron your body has in storage, the reserve it draws on between meals and through a heavy period.
Sold as Ferritin
female, age 18 and over
We look for 50 to 150 ug/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
Vaucher 2012 CMAJ randomised trial, with the WHO 2020 ferritin guideline
The floor of 50 comes from a randomised trial of iron for fatigue in menstruating women who were not anaemic. The ceiling of 150 is the WHO iron-overload flag for women.
male, age 18 and over
Convention puts this at 50 to 200 ug/L, which is not a guideline, so it is never drawn beside your result.
Convention. A convention rather than evidence, so we say the numbers in words and never draw them as a band.
WHO 2020 ferritin guideline, with BSG 2021
The ceiling of 200 is the WHO iron-overload flag for men and is well evidenced. The floor of 50 is extrapolated from the female trial data with no male trial behind it, which is why this row is a convention stated in prose rather than a band.
Folate circulating in your blood, which tracks what you have eaten over the last few days more than what your body has banked.
Sold as Folate
adults
We look for at or above 13.4 nmol/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
WHO serum and red cell folate thresholds
The floor is the top of the WHO possible-deficiency band. There is no figure above it: serum folate tracks recent intake, and the status marker is red cell folate, which this test does not include.
adults
We look for at or above 6 ug/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
WHO serum and red cell folate thresholds
The same threshold in ug/L. ug/L times 2.266 gives nmol/L.
A pituitary hormone that tells the ovaries or testes to do their work. In women it moves through the menstrual cycle.
Sold as FSH
female
No agreed tighter range
There is no agreed research range for FSH beyond the laboratory's. It changes across the menstrual cycle, and NICE NG23 says not to use it to identify the menopause from age 45.
male
No agreed tighter range
There is no agreed research range for FSH beyond the laboratory's. In men it is only interpretable alongside testosterone.
No agreed tighter range
There is no agreed research range for FSH beyond the laboratory's. What it means depends on sex, on the day of the cycle, and on what else was measured alongside it.
The ratio of your total testosterone to SHBG, used as a rough read of how much androgen is left unbound.
Sold as Free androgen index (calculated)
female
No agreed tighter range
There is no agreed research range for the free androgen index. It becomes unreliable once SHBG falls below 30 nmol/L, and combined hormonal contraception moves it mechanically by raising SHBG.
male
No agreed tighter range
There is no agreed research range for the free androgen index in men. BSSM recommends calculated free testosterone instead.
The active thyroid hormone, most of it converted from free T4 in the liver and other tissues.
Sold as Free T3
No agreed tighter range
There is no agreed research range for free T3 beyond the laboratory's. The best outcome study did not examine it, and UK laboratory intervals disagree with each other.
The main hormone your thyroid releases, in the unbound form your tissues can take up.
Sold as Free T4
No agreed tighter range
There is no agreed research range we can show for free T4 yet. The research figure depends on which assay the laboratory ran, and UK laboratory intervals for this marker differ widely, so we will add it once it is confirmed with our laboratory. Your laboratory's own range is the one to read this against.
The fraction of your testosterone that is not bound to carrier proteins, calculated from your total testosterone, SHBG and albumin.
Sold as Free testosterone (calculated)
male, age 18 and over, morning
We look for 225 to 1072 pmol/L.
Clinical guideline. A named clinical guideline sets this number.
BSSM 2023 threshold with the Jasuja 2023 reference interval
BSSM states that above 225 pmol/L does not require therapy. Must be Vermeulen-calculated. Where albumin is not measured the calculation assumes 43 g/L and the result is an estimate.
female
No agreed tighter range
There is no agreed research range for calculated free testosterone in women. The Vermeulen equation is poorly validated at the concentrations women run, and the 2019 global consensus states the evidence that the free fraction is the active one is lacking.
The proportion of your red blood cells that have sugar attached, which averages your blood glucose over about three months.
Sold as HbA1c
adults
We look for 31 to 38 mmol/mol.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
Selvin 2010 ARIC cohort, with NICE NG28 and WHO for the reference
5.0 to 5.6 percent in the old units. Not a lower-is-better marker: no benefit has been shown below 5.0 percent, and red-cell turnover moves it independently of glucose.
The particles that carry cholesterol back to the liver for disposal, a marker of how well that return traffic is running.
Sold as HDL cholesterol
male
We look for 1 to 2.4 mmol/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
Madsen 2017 Copenhagen cohorts with the NHS low-HDL threshold
Mortality was lowest around 1.9 mmol/L in men, and rose again above roughly 2.5 mmol/L, so the ceiling is real rather than decorative.
female
We look for 1.2 to 3.4 mmol/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
Madsen 2017 Copenhagen cohorts with the NHS low-HDL threshold
Mortality was lowest around 2.4 mmol/L in women, and rose again above roughly 3.5 mmol/L.
A protein the liver releases when something is inflamed, measured on an assay sensitive enough to pick up the low background level.
Sold as hs-CRP
adults
We look for 0 to 1 mg/L.
Clinical guideline. A named clinical guideline sets this number.
AHA and CDC 2003 scientific statement
The bands are the same for both sexes. Above 10 mg/L the number is not interpretable for cardiovascular risk and is worth repeating after two well weeks.
The iron circulating in your blood right now, on its way to the tissues that use it. It moves through the day and with what you last ate.
Sold as Iron
No agreed tighter range
There is no agreed research range for serum iron beyond the laboratory's. It varies by about a third across a single day and rises after food or an iron tablet, so it is read through transferrin saturation rather than on its own.
The cholesterol carried by the particles that can lodge in artery walls.
Sold as LDL cholesterol
adults
We look for at or below 3 mmol/L.
Clinical guideline. A named clinical guideline sets this number.
ESC/EAS 2019 dyslipidaemia guideline, low-risk goal
NICE sets no absolute figure for primary prevention. Tighter goals in the same guideline require an assessed risk category, which a blood test alone cannot give you.
An inherited variant of a cholesterol-carrying particle, set by your genes and stable for life.
Sold as Lp(a)
adults
We look for at or below 32 nmol/L.
Clinical guideline. A named clinical guideline sets this number.
HEART UK 2019 consensus statement
The consensus bands run 32 to 90, 90 to 200, 200 to 400 and above 400 nmol/L. Never converted from mg/dL: the conversion factor varies with the particle isoform.
A pituitary hormone that triggers ovulation in women and signals the testes to make testosterone in men.
Sold as LH
female
No agreed tighter range
There is no agreed research range for LH beyond the laboratory's. It swings sharply across the menstrual cycle, so a single reading depends heavily on the day it was taken.
male
No agreed tighter range
There is no agreed research range for LH beyond the laboratory's. In men it is only interpretable alongside testosterone.
No agreed tighter range
There is no agreed research range for LH beyond the laboratory's. What it means depends on sex and on what else was measured alongside it.
The small fraction of your body's magnesium that circulates in blood. Your kidneys hold this number steady, so it tells you less than people assume.
Sold as Magnesium
No agreed tighter range
There is no agreed research range for serum magnesium beyond the laboratory's. Under one percent of the body's magnesium is in the blood and the kidneys defend that level, so a result in the middle of the laboratory's range does not tell you what your intake has been.
Every cholesterol-carrying particle that can enter an artery wall, in one number.
Sold as Non-HDL cholesterol
adults
We look for at or below 3.4 mmol/L.
Clinical guideline. A named clinical guideline sets this number.
ESC/EAS 2019 dyslipidaemia guideline, moderate-risk goal
The guideline states no low-risk non-HDL goal, so 3.4 mmol/L is the loosest figure that exists in it. The NHS healthy level is 4.0 mmol/L.
A pituitary hormone best known for milk production, which also rises with sleep, exercise, a stressful blood draw and several common medicines.
Sold as Prolactin
No agreed tighter range
There is no agreed research range for prolactin beyond the laboratory's. A single raised reading needs repeating rather than reading, because sleep, exercise and the blood draw itself all move it.
The protein that binds testosterone and oestrogen in the blood and decides how much is left free. It moves with thyroid hormone, insulin and the contraceptive pill.
Sold as SHBG
No agreed tighter range
There is no agreed research range for SHBG beyond the laboratory's. Both ends carry signal and it is read alongside testosterone rather than on its own.
The pituitary signal that tells the thyroid how much hormone to make. It rises when the thyroid is running slow.
Sold as Thyroid (TSH)
age 18 to 70
We look for 1.5 to 3.5 mIU/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
Xu 2023 Lancet Diabetes Endocrinol individual-participant meta-analysis
Lowest cardiovascular and mortality risk sat at 1.90 to 2.90 mIU/L across 134,346 people. Widened here to 1.5 to 3.5 because within-person variation is about 20 percent, so a one-unit band is narrower than the noise. Population data, not a personal target. This points the opposite way to the convention that lower is better.
No agreed tighter range
Over 70 there is no agreed research range beyond the laboratory's. TSH rises with age, so a young-adult band would misread a normal older result.
The total amount of cholesterol your blood is carrying, protective and harmful particles counted together.
Sold as Total cholesterol
adults
We look for at or below 5 mmol/L.
Clinical guideline. A named clinical guideline sets this number.
NHS and HEART UK healthy level
No guideline sets a tighter total-cholesterol figure. The detail sits in non-HDL cholesterol and ApoB.
How much iron your blood could carry if every carrier site were filled. It is the same information as transferrin, expressed differently.
Sold as Total iron binding capacity (TIBC)
No agreed tighter range
There is no agreed research range for total iron binding capacity beyond the laboratory's. It is calculated from transferrin rather than measured, and two conversion conventions in UK use differ by about a tenth.
All the protein circulating in your blood, albumin plus the antibody and transport proteins.
Sold as Total protein
No agreed tighter range
There is no agreed research range for total protein beyond the laboratory's. A normal total can sit on top of a low albumin and a high globulin, so it is read alongside albumin.
The main androgen circulating in your blood, most of it carried bound to proteins. It peaks in the early morning and falls through the day.
Sold as Testosterone, Total testosterone
male, age 18 and over, morning
We look for at or above 12 nmol/L.
Clinical guideline. A named clinical guideline sets this number.
BSSM states that above 12 nmol/L does not require therapy. Needs an 08:00 to 11:00 sample. There is no research figure for an upper bound: laboratories typically report up to about 30 nmol/L, which is a reporting convention rather than a target, so read a high result against your laboratory's own ceiling. Do not age-adjust: BSSM reports that over 80 percent of men keep levels in range into old age.
female
No agreed tighter range
There is no agreed research range for testosterone in women. Eleven international societies state that serum testosterone must not be used on its own in women and that no cut-off separates one group from another. Your laboratory's range is the one to read this against.
The protein that carries iron around your bloodstream. Your body makes more of it when iron is scarce.
Sold as Transferrin
No agreed tighter range
There is no agreed research range for transferrin beyond the laboratory's. It rises when iron is scarce and on the combined pill, and falls with inflammation and liver disease.
What proportion of your iron carriers are actually loaded. It is the best single read of whether iron is reaching the places that need it.
Sold as Transferrin saturation
female
We look for 20 to 45 %.
Clinical guideline. A named clinical guideline sets this number.
EASL 2022 haemochromatosis guideline, with the RCP iron guidance
Below 20 percent is the recognised iron-deficiency threshold. Above 45 percent alongside a raised ferritin is the figure that prompts a GP conversation in women.
male
We look for 20 to 50 %.
Clinical guideline. A named clinical guideline sets this number.
EASL 2022 haemochromatosis guideline, with the RCP iron guidance
Below 20 percent is the recognised iron-deficiency threshold. Above 50 percent alongside a raised ferritin is the figure that prompts a GP conversation in men.
The fat your blood is transporting between meals and storage, which rises with recent food, alcohol and excess carbohydrate.
Sold as Triglycerides
fasting
We look for at or below 1.7 mmol/L.
Clinical guideline. A named clinical guideline sets this number.
ESC/EAS 2019 dyslipidaemia guideline
The fasting desirable threshold. There is no defensible lower bound.
non-fasting
We look for at or below 2 mmol/L.
Research studies. Cohort or trial evidence supports it, but no guideline states it. Association is not cause.
EAS and EFLM non-fasting lipid consensus
The default for a posted finger-prick kit, which is usually taken without fasting.
The waste product your liver makes from used protein and your kidneys clear, so it moves with both protein intake and hydration.
Sold as Urea
No agreed tighter range
There is no agreed research range for urea beyond the laboratory's. It moves with protein intake and hydration before it moves with kidney function.
The fraction of your B12 that is bound to the carrier your cells can actually take up. Roughly a fifth of the total, and the part that matters.
Sold as Vitamin B12
age 16 and over
We look for at or above 70 pmol/L.
Clinical guideline. A named clinical guideline sets this number.
NICE NG239 (2024) and NICE MIB40
Active B12, also called holotranscobalamin. It runs on a completely different scale to total B12: 70 pmol/L is healthy here and would be very low there. The laboratory's interval is assay dependent.
The total B12 in your blood, most of which is bound to a carrier your cells cannot use. It is the standard first-line test and it is a blunt one.
Sold as Vitamin B12
age 16 and over
We look for at or above 258 pmol/L.
Clinical guideline. A named clinical guideline sets this number.
NICE treats 133 to 258 pmol/L as indeterminate, so a figure a laboratory prints as normal can still sit in that band. There is no upper research figure.
age 16 and over
We look for at or above 350 ng/L.
Clinical guideline. A named clinical guideline sets this number.
The same thresholds in the unit most UK laboratories report. ng/L and pg/mL are identical, and ng/L times 0.7378 gives pmol/L.
The circulating store of vitamin D your body draws on, built from sunlight on skin and from what you eat or supplement.
Sold as Vitamin D
adults
Convention puts this at 75 to 125 nmol/L, which is not a guideline, so it is never drawn beside your result.
Convention. A convention rather than evidence, so we say the numbers in words and never draw them as a band.
Endocrine Society 2011, alongside SACN 2016 and ROS 2018
UK guidance sets sufficiency at 50 nmol/L, and that figure is the well-evidenced one. The 75 to 125 band is a convention from a different jurisdiction, so it is stated in prose next to the UK figure and never drawn as a band. ng/mL times 2.5 gives nmol/L.
This page is generated from the same table the results screen reads, so it cannot drift from what you were shown. The guidelines behind every panel covers what each panel measures and why.
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