Commonly used blood tests and what they mean

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See also Biochemistry - interpretation


Poor interpretations have led to some serious mistakes throughout history. Even St Jerome, the patron Saint of translators fell victim: he translated the Old Bible from Hebrew and made a simple error concerning the moment when Moses came down from Mount Sinai, with his head in “radiance”. In Hebrew: “karan” is radiance, but because Hebrew is written without vowels, St. Jerome read ‘karan’ as “keren” which means “horned”. Because of this mistake there are many paintings and sculptures of Moses with horns. See Five Fun Facts about St Jerome. More recently, in 1980 Willie Ramírez was admitted to a Florida hospital in a comatose state. At the time of admission, an interpreter translated the Spanish term “intoxicado” which means poisoned or having had an allergic reaction as “intoxicated”. Willie, who was suffering from an intracerebral haemorrhage was treated for an intentional drug overdose. As a result, he was left quadriplegic. This resulted in a $71million malpractice suit. See 'A translation error that cost 71 million dollars' Other examples of poor interpretation include:

Poor interpretations from History

Speaker What they said / intended How it was interpreted
Jimmy Carter speaking to a Polish audience “…I have come to learn your opinions and understand your desires for the future…” “I desire the Poles carnally…”
HSBC marketing campaign “Assume nothing” “Do nothing”
Japanese Prime Minister Kantaro Suzuki – referring to the Potsdam conference in 1945 – the heads of Government of the UK, USA and USSR held this conference– to consider post-war order, the formal peace treaty and countering the effects of the war…as these 3 issues concerned the defeated Germany – the conference ended 2 August 1945 “No comment. We are still thinking about it” “We are ignoring it in contempt”.

On 6 August 1945 – 4 days after this comment was mis-translated - the American bomber ‘Enola Gay’ dropped a five-ton atomic bomb over the Japanese city of Hiroshima.

During Richard Nixon’s visit to China in 1972, Chinese premier Zhou Enlai famously said it was ‘too early to tell’ when evaluating the effects of the French Revolution. Zhou Enlai was referring to the 1968 riots in Paris. The comments were interpreted as referring to the French Revolution in 1789 and the western Press inferred great wisdom in the Chinese Premier’s words and compared how the East always takes the long view as opposed to the shabby short-term West!
Italian astronomer Giovanni Virginio Schiaparelli mapped Mars in 1877, calling dark and light areas on the planet’s surface as ‘seas’ and ‘continents’ and labelling what he thought were channels with the Italian word ‘canali’. Virginio was trying to describe what he saw in everyday language. Canali was mistranslated as ‘canals’ and there followed a belief that ‘life on Mars’ had been established. Even respected figures such as US astronomer Percival Lowell mapped hundreds of these ‘canals’ between 1894 and 1895 and published three books on Mars with illustrations showing what he thought were artificial structures built to carry water by a brilliant race of engineers.


This page really should not be necessary. But I daily see medical tests that have been poorly interpreted so vital clues are missed. This is for several reasons:

  • If a test result lies within the reference ranges the patient is told it is normal and no action required. However, reference ranges reflect population averages – but some individuals will function best at top end of range, some at low end of range.
  • Population ranges may not reflect normal ranges. Ranges are arrived at by measuring the current population, which may not be normal! The best example is levels of T4 in the blood – my lab’s ref range is 12-22pmol/l but some NHS labs have ranges as low as 7-14. This will result in missing many cases of secondary hypothyroidism. Population ranges and averages are not normal ranges and averages!
  • A normal blood sugar used to be 4-6.8mmols/l but now levels up to 11 are considered satisfactory.
  • A range may be negatively skewed [see graph below]. A normal range for a white cell count is often 4-11. But most run normally at 4-5. A white cell count running at 8-11 may point to chronic inflammation. So, one might fall in the normal range but in the negative skew case, one is likely to be near the top end of the scale, and this may not be optimal.

The key point is that tests are there to narrow the diagnosis, not to make it. All diagnosis is hypothesis which then depends on response to treatment. All diagnosis is retrospective!

Graph of a negatively skewed distribution

Negative skew - A distribution is skewed if one of its 'tails' is longer than the other. The distribution below has a negative skew since it has a long tail in the negative [left] direction:

Negative skew.png

Commonly done tests which I often see badly interpreted

This list is by no means exhaustive!

Test Significant result What it means Action
Full blood count Low haemoglobin Anaemia. This is either because you are losing blood OR you are not making it fast enough because you are deficient in a raw material or lacking the energy for manufacture Do faecal occult blood to check for gut losses…. and faecal calprotectin both of which may indicate pathology. See Faecal calprotectin test

?heavy periods Ferritin to check for iron deficiency Measure B12

High haemoglobin Smoker

Polycythaemia rubra vera Carbon monoxide poisoning

Stop smoking and recheck

See a doctor

MCV (Mean corpuscular volume) is high Either you are hypothyroid.... You need to do thyroid function tests. See Thyroid test
OR a poor methylator - see The Methylation Cycle Measure homocysteine. See Homocysteine - the biochemistry of - not essential reading but interesting! It is possible your GP can do this test. High homocysteine is a risk factor for fatigue but also arterial disease, cancer and dementia. SO, this is an important test not least of all because if positive then we must screen all first degree relative as high homocysteine runs in families
Postal delay between blood taking and blood testing may cause a false macrocytosis (enlargement of red blood cells). Check time between sample taking and testing
MCV (mean corpuscular volume) low Iron deficient?


Check ferritin
WCC (white cell count) a bit high The normal rage is positively skewed (see above for definition of skew), so I expect to see a result of 4-6…… Wait and repeat. If constantly high, then look for cause of inflammation
Low WCC White cells being used up fast to fight infection AND/OR

Lack of raw materials AND/OR lack of energy to make white cells

Improve energy delivery mechanisms - see My book “Diagnosing and treating Chronic fatigue syndrome and myalgic encephalitis: it's mitochondria not hypochondria”

Improve nutritional status Identify the infection (see My book "The Infection Game - life is an arms race") – the commonest offenders in CFS are EBV, Lyme and mycoplasma

ESR (erythrocyte sedimentation rate) I like to see this below 5! Mild inflammation but this result does not tell us why
HDL % [High-density lipoprotein]

(calculated by dividing HDL cholesterol by total cholesterol)

The percentage of the friendly HDL is low. HDL is being used up in the business of healing and repairing arteries – ie they are being damaged by something. This may be metabolic syndrome and/or high homocysteine and/or chronic inflammation. Put in place interventions then repeat test to check progress. The higher this result the better- on a good PK diet I expect this to be 40%.
Electrolytes Sodium low Lack of salt in diet

Salt losing state eg diuretics or kidney failure

On a PK diet the need for salt increases – aim for 4 grams daily (1 teaspoonful of Sunshine salt). See My book - Paleo-Ketogenic: The Why and The How and Ketogenic diet - the practical details
Potassium high Delay in transport – K easily leaks out of cells Linguistic Note – why is the symbol for potassium ‘’K’’ – ‘’Potassium’’ is derived from the English word potash. The chemical symbol K comes from ‘’kalium’’, the Mediaeval Latin for potash, which may have derived from the arabic word qali, meaning alkali. Interested readers should see Symbol (Chemistry) Wikipedia article
Potassium low Too little in diet The body cannot store potassium – you have to eat it daily – plenty in PK diet

See Sunshine salt

Serum magnesium Rarely done. Not a reliable test of body stores. Most doctors do not understand the difference between a serum magnesium and a red cell magnesium. Serum levels must be kept within a tight range, or the heart stops. Therefore, serum levels are maintained at the expense of levels inside cells. See Magnesium test - whole blood Ignore if normal.

If low, then you are in serious trouble and need urgent medical attention

Creatinine high High protein diet and/ or high muscle mass

Poor kidney function

Reduce protein intake and recheck

Look for causes of kidney damage

Creatinine low Low protein diet and/ or low muscle mass
Urea high Dehydrated

May accompany high creatinine

You need water AND fat AND salt to be properly hydrated
Uric acid high Uric acid is a mycotoxin Look for a fungal issue - see Chronic Fungal Infection as a cause of disease: the toxicity of mycotoxins
Uric acid is an antioxidant May indicate poor anti-oxidant status - see Antioxidants and Antioxidant status profile
12 hour Fasting glucose 4.0-5.6 (ideally lower than 5.0) If higher you are on the way to diabetes
Glycosylated haemoglobin A very useful test of average blood sugar over the past 3 months. Ranges have changed recently because nearly all Westerners eat too much carb and are on the way to diabetes. How can the NHS deal with this? Move the goal posts.
Should be 22-38. The lower the better. On a good PK diet this may be less than 20
Liver function tests GGT (gamma-glutamyl transpeptidase) ALT (alanine transaminase) AST (aspartate aminotransferase) a bit high.

Alkaline phosphatase high. See Footnote for alkaline phosphatase low

Enzyme induction to deal with toxins

This is not liver damage. Tissue damage – liver, gallbladder, bones

From alcohol or other such drugs.

From toxins from the outside world. Products of the upper fermenting gut. Find the cause.

LDH (lactate dehydrogenase) high May be any tissue damage in the body commonly of liver, bones, heart kidney. What is the cause of?
I suspect where there are poor energy delivery mechanisms (see My book “Diagnosing and treating Chronic fatigue syndrome and myalgic encephalitis: it's mitochondria not hypochondria” ) with early switch in into anaerobic metabolism, this enzyme is induced Improve energy delivery mechanisms - see My book “Diagnosing and treating Chronic fatigue syndrome and myalgic encephalitis: it's mitochondria not hypochondria”
Bilirubin I like to see the bilirubin below 10. When it is above 19 this is called Gilbert’s syndrome. This means you are a slow detoxifier and will be more susceptible to toxic stress. Identify the cause of the toxic stress and mitigate - see Detoxification - an overview.

Take glutathione 250mgs for life to improve liver detox

Bone Low calcium Vitamin D deficiency. If you are not taking vitamin D, then you will be deficient! Sunshine salt has 5,000iu of vit D per 5gram daily dose
Normal “bone markers” does not exclude osteoporosis The best test for osteoporosis is a heel bone density scan which is accurate and involves no dangerous X rays
Ferritin low You are iron deficient. Either you are losing blood OR lacking iron. This may be due to lack of iron in the diet (meat) OR malabsorption. You need an acid stomach to absorb iron. One cause of this is upper fermenting gut due to too much carb in the diet
PSA - Prostate specific antigen High. PSA reflects the amount of prostate tissue. It is the rate of change that suggests malignancy. Do the PK diet. The growth promotors are carbs and dairy.

Recheck in one-month intervals to see the rate of change.

B12 normal Normal ranges simply reflect that to prevent pernicious anaemia A normal B12 never predicts a response to B12 by injection
Homocysteine - see Homocysteine - the biochemistry of - not essential reading but interesting! I like to see this below 10

(many lab ref ranges are less than 15)

High homocysteine means poor methylation. This is an essential biochemical tool to allow one to “read” DNA, to detoxify, to synthesise enzymes and proteins and much more! Being a poor methylator is a MAJOR risk factor for arterial disease, dementia, cancer and degenerative disease. To normalise you need methylated B vitamins.
Thyroid TSH Low or normal TSH never excludes the possibility of secondary hypothyroidism due to poor pituitary function A TSH tells us little but it is relied upon too heavily by many doctors to determine the dose of thyroid hormone. See Thyroid - the correct prescribing of thyroid hormones
Free T4 Check the ref range. My lab is 12-22. Some NHS ranges are 7-14. But some do not feel well until running at 30pmol/l.
Free T3 Ditto above Ditto - you may only feel well, running 'high' levels
If T3 is low compared to T4. This suggests poor conversion of inactive T4 to the active T3 …… T3 hypothyroidism.

You may need a T3 supplement

High reverse T3 This points to thyroid hormone receptor resistance – in this event the blood tests are not helpful – You must rely on the clinical picture to determine the dose of thyroid hormone
If TSH is high despite good levels of T4 and T3 then this points to Thyroid hormone receptor resistance

Footnote re alkaline phosphatase low Hypophosphatasia (HPP): HPP is a very rare genetic disorder, which often goes undiagnosed. A marker for this condition is low ALP. Other conditions such as coeliac disease, pernicious or profound anaemia, multiple myeloma, hypothyroidism, Cushing’s syndrome and milk alkali syndrome can also sometimes cause low ALP. Please see this very useful website for more detail on HPP: Rare Diseases - HPP. Research into HPP is sparse but there is some indication of the involvement of mitochondrial dysfunction - see Tissue Nonspecific Alkaline Phosphatase Function in Bone and Muscle Progenitor Cells: Control of Mitochondrial Respiration and ATP Production. Int J Mol Sci 2021; 22(3): 1140. Treatment is with vitamin D3 (10,000 iu daily) and possibly magnesium (300 mg daily) also - see Vitamin D metabolism in hypophosphatasia. Acta Paediatr Scand 1982; 71(3): 517-521.

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