Blood tests

2025 March 8th

Once upon a time, I was afraid of needles. Seriously, hold me down whilst I look firmly away afraid of needles. I sort of got over it around 15 years ago when I had a bad case of flu as well as needing to have some travel vaccinations, so I grit my teeth and learned to behave whilst needles were usually stuck into my left arm - and as I never got any exotic lurgies whilst working in India or Malaysia, nor have ever had a bad case of influenza again, it was worth it. Covid reinforced that as nobody but a complete idiot wanted to skip that jab, and indeed I kept going with optional paid-for covid and flu jabs when the NHS in its wisdom decided that I was no longer vulnerable enough to need them, and thus get them for free. Bizarely whilst the flu jab always remained available - usually about £15 in my local pharmacist, I had to hunt online for anybody who’d take my money for a covid jab, then drive around 20 miles out of my way to get it. I found that absolutely bizarre - the sudden switch from “everybody must have the jab” to “you can only have it if we decide, but then it’ll be free” - one of many bits of completely disjointed thinking in this country over that particular disease.

Anyhow, nowadays, I have cancer, I’m in the middle of chemotherapy, I’ve completely lost track of the number of needles stuck into me either to put chemicals in, or take blood out now. And frankly I’ve become pretty blase about it. But that has also brought something else to my head - just what are all these blood tests about and what do they mean. Well conveniently the NHS has actually become pretty good at at-the-very-least telling you what they have done, if sometimes less good at telling other bits of the NHS, as evidenced by the delay every time I go for chemo whilst they track down the previous Friday’s results. But for me personally, it’s actually all on an app. So I thought I’d take a look.

My most recently blood tests were done at my local hospital - Amersham Hospital, about 7 minutes drive away, 9 days ago, and all the results jumped onto my phone about 48 hours later. So let’s take a look at these, what I can find out about why they were measured, and what it means.

(1) Haemoglobin estimation test. Result 123 g/L, normal range 130 to 180 g/L

So apparently I’m a bit low, but not excessively so. The experts comment here is that it’s “stable”, and indeed I can check a previous test on 7 February (128 g/L). My inner research scientist would tend to regard that sort of small change as within experimental error, but it does tell me that my haemoglobin readings are a little on the low side. Reading up, I’m going to hazard a guess that this is because the chemotherapy is attacking my bone marrow where the red blood cells are produced, and hence it’s a bit low. I’d hazard an uninformed guess that if this dips significantly, somebody’ll start worrying about it, but not yet.

(2) Urea and electrolytes. Sodium 141 mmol/L, normal range 136-145 mmol/L. Potassium 3.8 mmol/L, normal range 3.5 to 5.1 mmol/L. Urea 8.4 mmol/L, normal range 3.2 to 7.4; ooh that’s a bit high, let’s come back to that in a minute. Creatinine 97 μmol/L, normal range 63 to 111.

So, I know what moles are - it’s a fixed number of molecules. Specifically it’s Avogadro’s number, or 6.022×10^23 molecules. So that 97 micro-moles/litre is still 58,413,400,000,000,000,000 molecules of something called creatinine per litre of my blood. That’s a lot of molecules! (See Mr Larkham, I was paying attention to at least some of what you said in A-level chemistry 37 years ago!) What these are is a bunch of chemicals used in my blood to drive a set of physical processes keeping me alive and functioning properly. Doubtless hundreds of research scientists over decades, possibly a century or more, have done all the work to understand what each does for me, or anybody else. The medical expert comments on each all seem happy, but I’d like to dip into the Urea reading.

Let’s ask the great modern oracle, ChatGPT. Well it says this…

What High Urea Levels May Indicate (Uremia)

Kidney Dysfunction: Reduced kidney filtration due to chronic kidney disease (CKD), acute kidney injury (AKI), or kidney failure.

Dehydration: Low fluid levels concentrate urea in the blood.

High Protein Intake: Excess dietary protein increases urea production.

Heart Failure: Reduced blood flow to kidneys can affect filtration.

Shock or Severe Infection: Impaired circulation can cause kidney dysfunction.

Gastrointestinal Bleeding: Breakdown of blood proteins increases urea.

Certain Medications: E.g., diuretics, steroids, or tetracyclines.

Next Steps

If serum urea levels are abnormal, doctors usually consider creatinine levels alongside urea to assess kidney function more accurately. High urea with high creatinine often indicates kidney issues, while isolated high urea might be due to diet, dehydration, or other factors.

Well there you go. I know I’ve been increasing my protein intake, and I know I’m taking steroids. I also know my creatinine levels are fine. So there you probably have an answer to why nobody’s panicking about this. So I won’t either. What else have we got…

(3) Liver Function Tests. Serum total protein 64g/L, normal range 64 to 83 g/L. Serum albumin, 39 g/L, normal range 39 to 50 g/L. Serum ALT level 19 U/L, normal range 10 to 35 U/L. Serum alkaline phosphatase, 110 U/L, normal range 40 to 150 U/L. Serum bilirubin level 9 umol/L, normal range 0 to 21 umol/L. Serum globulin range 25 g/L, normal range 20 to 39 g/L.

Okay this is apparently fine, but there are a few words I’ve never seen before. What is ALT, presumably other than a button near the bottom of my keyboard. Well I asked the NHS app and it denied all knowledge again, so back to ChatGPT…

ALT (Alanine Aminotransferase) in Blood Test Results

ALT (Alanine Aminotransferase) is an enzyme found primarily in the liver. It plays a key role in amino acid metabolism and is released into the bloodstream when liver cells are damaged.

Normal ALT Range

Men: 10–40 U/L

Women: 7–35 U/L

(Ranges may vary slightly depending on the laboratory.)

Thank you OpenAI, I consider myself educated. And not at-all worried, but I like to know.

In blood test readings, the "U" in U/L stands for "units", and U/L means units per liter.

Explanation:

"U" (Units): Represents an amount of enzyme activity rather than a specific quantity of the enzyme itself.

"/L" (Per Liter): Indicates the concentration of the enzyme in one liter of blood.

Well I’ve been educated, not at all worried, but definitely educated. Albeit that it’s “litre” in British English !

By the way there’s another word there I’ve never seen before. Bilirubin - what the heck is that? A bit of googling this time tells me that it’s an indication of the rate of ongoing breakdown of my red blood cells. Fair enough, that’s normal as well then. What else have these tests got to tell me?

(4) Bone Profile. Serum calcium 2.19 mmol/L, normal range 2.10 to 2.55. Serum inorganic phoshate, 1.10 mmol/L, normal range 0.8 to 1.5 mmol/L. Serum adjusted calcium concentrate 2.21 mmol/L, normal range 2.10 to 2.55 mmol/L.

Okay, so they’re checking the condition of my bones and they’re apparently fine. Hell though, they really aren’t mucking about with these tests are they? What’s next…

(5) Prostate Specific Antigen, or PSA. Ooh, we’d like to know about this wouldn’t we. So I had a look at both now and the history. This is the reading that got me down this whole road after all.

28 February 2025, 0.14 ng/mL

7 February 2025, 0.25 ng/L

28 October 2024, 34 ng/L

12 September 2024, 28 ng/L

Normal range for my age - 0 to 3.5 ng/L.

So it was abnormally high, but since I started chemo it has absolutely plumeted down to a value so safe it’s barely measurable. Fantastic, I’ll take that, but at some point I think I want to do a bit more digging to understand what it’s really telling me. Not today though.

(5) Serum magnesium level, 0.89 mmol/L, normal range 0.70 to 1.00. Whatever that’s all about, it’s middle of the range - I’ll take it.

(6) GFR calculated abbreviated MDRD test, 70 mL/m/1.73m No range. Okay, what the hell does that mean. Let’s go to ChatGPT again…

GFR (Glomerular Filtration Rate) - MDRD Calculation

The GFR (Glomerular Filtration Rate) is a measure of how well the kidneys filter waste from the blood. The MDRD (Modification of Diet in Renal Disease) formula is a method used to estimate GFR based on serum creatinine levels and other factors.

What Does the MDRD GFR Test Measure?

It estimates kidney function and helps diagnose chronic kidney disease (CKD).

The higher the GFR, the better the kidneys are functioning.

A low GFR suggests reduced kidney function.

How is MDRD GFR Calculated?

The MDRD equation estimates GFR using:

Serum creatinine (waste product filtered by the kidneys)

Age (GFR declines with age)

Sex (men typically have higher GFR than women)

Race (some versions include a correction factor for African American individuals)

Normal GFR Range

≥ 90 mL/min/1.73m² → Normal kidney function

60–89 mL/min/1.73m² → Mildly decreased function

30–59 mL/min/1.73m² → Moderate kidney disease (Stage 3 CKD)

15–29 mL/min/1.73m² → Severe kidney disease (Stage 4 CKD)

< 15 mL/min/1.73m² → Kidney failure (Stage 5 CKD)

What Does a Low MDRD GFR Mean?

Early kidney disease (if GFR is between 60–89)

Chronic kidney disease (CKD) (if GFR is < 60 for more than 3 months)

Severe kidney damage or failure (if GFR < 15)

So in a nutshell, I have *slightly* reduced kidney function. Checking the history it’s been bouncing around this value ever since I was first tested in September. Should I worry about this? Presumably not or somebody would have mentioned it. I asked ChatGPT about that as well, and it said…

Interpretation of a GFR of 70 in a 54-Year-Old Man

Mildly reduced kidney function but not necessarily a concern if no symptoms or other kidney-related issues (e.g., protein in urine, high creatinine).

GFR naturally declines with age, and a GFR of 70 is fairly common in people over 50.

No immediate kidney failure risk but worth monitoring over time.

Okay, I’ll take that. Keep an eye on it, don’t worry.

So there you go. You now know more than I do ! That was a heck of a lot of blood test parameters - sixteen in total. I feel rather reassured not only at how much they’ve looked into, but at my own amateur attempt to interpret it.

Sometimes soon I feel the need to read more about PSA especially and try and understand it better. But for now, have a lovely weekend.