There is something slightly unnerving about opening your blood test results and seeing a page full of numbers, abbreviations and words that seem to belong to another language.
Hb.
WBC.
ALT.
eGFR.
TSH.
Then there are numbers with little arrows pointing up or down.
And the first thought is usually:
“Is something wrong with me?”
As a pharmacist, I see this quite often. People bring their blood results into the pharmacy and ask me to explain what they mean.
The good news is that many of the common blood tests are actually quite straightforward once you understand what they are looking for.
A blood test is simply a way of giving your doctor a snapshot of what is happening inside your body. It can help detect illness, monitor an existing condition or check whether a medicine is working safely. (nhs.uk)
Here are some of the common results you are likely to come across.
Full Blood Count — FBC
This is one of the most common blood tests.
It looks at the different cells circulating in your blood.
Haemoglobin — Hb
Haemoglobin is the substance inside red blood cells that carries oxygen around your body.
If your haemoglobin is low, you may have anaemia.
People with anaemia can experience tiredness, weakness, breathlessness or looking unusually pale, although symptoms vary considerably.
Iron deficiency is one possible cause, but it is certainly not the only one.
A high haemoglobin can occur for several reasons, including dehydration or living at high altitude, so one abnormal result does not automatically mean there is a serious problem.
White blood cells — WBC
White blood cells are part of your immune system.
A high white cell count can occur when your body is fighting an infection or inflammation. Certain medicines and other conditions can also affect it.
A low count can have several causes, including some medicines, viral infections and problems affecting the bone marrow or immune system.
The important point is that the white cell count does not tell you exactly what the problem is. It gives your doctor a clue.
Platelets
Platelets help your blood clot.
Too few can increase the tendency to bleed, while too many can sometimes be associated with an increased risk of clotting.
Again, doctors look at the result alongside your symptoms and the rest of the blood count rather than treating one number in isolation.
HbA1c — your longer-term blood sugar
If you have had a diabetes check, you may have seen something called HbA1c.
This is different from the finger-prick blood sugar reading you might take at home.
HbA1c gives an indication of your average blood glucose levels over the previous few months.
In UK practice, an HbA1c of 48 mmol/mol (6.5%) or above is in the diabetes range when used for diagnosis, although an unexpected result in someone without symptoms generally needs confirmation. Results of 42–47 mmol/mol indicate an increased risk of developing diabetes. (Nice)
For someone who already has diabetes, however, the number is interpreted differently. Your individual target may not be the same as somebody else’s.
So don’t look at another person’s HbA1c and assume that your target should be identical.
Cholesterol — more than just one number
When people say, “My cholesterol is 6,” they are often talking about their total cholesterol.
But cholesterol testing can give you considerably more information.
LDL
LDL is often described as the “bad” cholesterol.
Too much LDL can contribute to fatty deposits building up inside the arteries.
Generally, lower LDL is better, but the appropriate target depends heavily on your individual cardiovascular risk and whether you already have cardiovascular disease.
HDL
HDL is often called the “good” cholesterol because it helps transport cholesterol away from tissues and back towards the liver.
Non-HDL
This is another figure you may see on your results.
It is essentially your total cholesterol minus HDL and includes the cholesterol carried by several potentially harmful particles.
Triglycerides
These are another type of fat circulating in the blood.
They can be affected by diet, weight, alcohol, diabetes and other medical conditions.
For a healthy adult, the NHS gives general guide levels of total cholesterol below 5.0 mmol/L, LDL below 3.0 mmol/L, HDL above 1.0 mmol/L in men and 1.2 mmol/L in women, and non-HDL below 4.0 mmol/L. But these are general healthy-adult guides, not personalised targets. (nhs.uk)
If you already have heart or vascular disease, your doctor may want your LDL considerably lower.
Kidney tests — creatinine and eGFR
Your kidneys are constantly filtering waste products from your blood.
Two results you will commonly see are creatinine and eGFR.
Creatinine
Creatinine is a waste product produced by normal muscle activity.
Your kidneys normally remove it from the blood.
If the kidneys are not filtering properly, creatinine can rise.
But creatinine is influenced by things such as muscle mass and hydration, so it is not interpreted on its own.
eGFR
This stands for estimated glomerular filtration rate.
In simple terms, it is an estimate of how well your kidneys are filtering your blood.
A lower eGFR can indicate reduced kidney function, but one slightly low result does not automatically mean you have chronic kidney disease.
Doctors look at the result over time and may also check your urine for protein or blood. (nhs.uk)
That is why I always tell people:
Don’t panic over one kidney number. Look at the trend.
Urea and electrolytes — U&E
This group of tests commonly includes substances such as sodium and potassium, as well as urea and creatinine.
Sodium
Sodium helps control the body’s fluid balance and is important for nerves and muscles.
Both a low and a high sodium level can have many possible causes.
Potassium
Potassium is particularly important for muscles and the heart.
Abnormally high or low potassium can sometimes be serious, which is why doctors pay close attention to it.
Dehydration, kidney problems and some medicines can all influence electrolyte levels.
Liver blood tests — LFTs
Despite the name, liver function tests are not one single test.
They are a collection of blood tests that can give information about the liver and bile ducts.
ALT and AST
These are enzymes found inside cells.
When liver cells are irritated or damaged, levels can rise.
However, an abnormal ALT or AST does not automatically mean you have liver disease. Several things can affect these enzymes, including medicines and other conditions. (SPS - Specialist Pharmacy Service)
ALP
ALP can be associated with the liver and bile ducts, but it is also found in bone.
That is important because a raised ALP does not necessarily mean the problem is coming from the liver.
GGT
GGT is another enzyme associated particularly with the liver and bile ducts.
It can be raised for a number of reasons, including alcohol use and some liver conditions.
Bilirubin
Bilirubin is produced when old red blood cells are broken down.
The liver processes it and excretes it in bile.
A high bilirubin level can sometimes result in jaundice — yellowing of the skin or whites of the eyes.
But, as with most blood tests, the result needs to be considered alongside the other liver tests.
Thyroid tests — TSH and T4
Your thyroid produces hormones that influence many aspects of how your body works.
The two results you are most likely to encounter are TSH and T4.
TSH stands for thyroid-stimulating hormone.
In very simple terms, the brain uses TSH to tell the thyroid how hard to work.
A high TSH can be associated with an underactive thyroid.
A low TSH can be associated with an overactive thyroid.
T4 is one of the main thyroid hormones.
The combination of TSH and T4 helps the doctor work out what is happening.
If you take levothyroxine or another thyroid medicine, these tests are also used to make sure your treatment is appropriately adjusted.
CRP — inflammation
You may also see CRP, which stands for C-reactive protein.
CRP is a marker of inflammation.
It can rise when the body is responding to infection, inflammation or tissue injury.
But CRP is not a diagnostic test for one particular disease.
Think of it more as a warning light on the dashboard.
It tells the doctor that something may be causing inflammation, but further investigation may be needed to find out what.
Vitamin B12, folate and vitamin D
These are commonly tested when there is a particular reason to suspect a deficiency.
Low B12 or folate can contribute to anaemia and other problems, including neurological symptoms in the case of B12 deficiency.
Vitamin D is important for bone and muscle health, and levels may be checked in people where deficiency is suspected.
But don’t assume that every vitamin result needs to be at the absolute top of the laboratory range.
More is not automatically better.
One thing I wish everyone knew about blood tests
An abnormal result does not automatically mean you are ill.
And a result inside the laboratory’s reference range does not guarantee that everything is perfect.
Blood tests have to be interpreted in context.
Your age, sex, medical history, medicines, symptoms, recent illness, hydration and even whether you had eaten before the test can sometimes affect the result.
Most importantly, doctors look at patterns and trends.
For example, a kidney result that has gradually changed over several years can tell a very different story from a single mildly abnormal result.
The same applies to liver tests, blood counts, cholesterol and many other measurements.
So the next time you receive a blood test report and see a little arrow pointing upwards, don’t immediately reach for Google and convince yourself that you have the worst disease imaginable.
Take a breath.
Look at the actual test.
Look at the reference range provided by the laboratory.
And, most importantly, ask what the result means in your particular situation.
As I often tell people in the pharmacy, a blood test is a piece of the puzzle.
It is rarely the whole picture.
Until next time, stay well.
This article is for general health education and is not a diagnosis or a substitute for advice from your GP or healthcare professional. Reference ranges vary between laboratories and personalised treatment targets may be different from general population ranges.
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