Kidney function blood test result - worried

[Tabaxi]

Hi, hoping someone can reassure me. I’ve got myself into a bit of a state worrying and haven’t told anyone in real life.

About a month ago I had a sore little toe, which came on in the middle of the night. It was red, but not swollen. Went to GP and the nurse said maybe it was gout, so she asked me to book in for bloods a month later. I had the blood test this week.

She also prescribed Naproxen, but I didn’t take it because it took a little while to come in, and when it was ready to collect the toe was no longer sore. I did take ibuprofen, though. I have also taken ibuprofen more often than paracetamol since about September, due to back pain and a leg injury. I don’t take it every week but have had a couple of spells where I have taken it for about a week.

All my bloods were fine except creatinine, which was 104 umol/L, giving an eGFR of 54. The nurse said we needed to repeat the test at the end of February. She said it could have been caused by Naproxen or
dehydration. But as I said, I did not actually
take the Naproxen.

If it’s relevant, I am quite an active person. I exercise 5 days per week including weight training. I did weight training on the Sunday before the test, though it was only a 20-minute session. The blood test was first thing in the morning (7.40am), and the night before I had a large glass of red wine plus a roast chicken dinner. The morning of the test I ate porridge made with milk, plus a cup of tea and small glass of orange juice, and a couple of sips of water. This was about 30 mins before the test.

On Saturday and Friday we also had meat, which was somewhat unusual as we normally eat meat maybe once a week or once every 10 days. I eat a lot of dairy, probably too much, and eggs quite often as well.

i guess what I am asking is whether any of my lifestyle factors or the things I have eaten recently could have affected this result? All my other results were normal, including the liver function test, which showed a normal level of albumin in my blood.

Since I was “only” getting checked for gout I’m pretty thrown by all of this and quite worried so if anyone is able to help me shed any light I’d really appreciate it. The check for gout also didn’t show up anything so the toe is a mystery as well (but I am less worried about that).

Edited to add: I’m female, pretty slim and almost 50. Muscular legs, skinny upper body.

I had a similar test and my eGGR of 70. Funny enough, I initially went because I'm feeling numbness in some of my toes. From my limited research, I know that a lot of protein can decrease levels. Have you increased that at all recently as part of a health kick?

It's worth noting that mine went back up to 90 on my re-test. However, I am back to the doctors this afternoon as my other toe has started to go numb also. So I presume they'll do a re-test on all my bloods.

I don’t know anything about kidney function, but I am on my third kidney function blood test due to high creatinine levels.
I know it’s diet related though - I eat high protein and I take creatine daily.

How out of the safe zone are your creatinine levels?

Thanks for replying and I hope you get answers about your toes.

I wouldn’t say I’ve deliberately increased protein recently but over Christmas and New Year I ate far more meat than normal. I often also have 2 boiled eggs with toast at lunchtime. And I probably eat a bit too much milk, cheese and yogurt (though I’ve not had any yogurt since before Christmas - usually have it most evenings though).

@Newyeargymwanker I think for a woman the level is supposed to be up to 90, but mine was 104.

I don’t think they consider this to be dangerously high but it is higher than it should be.

have they suggested drinking more water before the next one?

That’s what I am trying to do as I weight train a lot and don’t want to make any dietary changes.

Yes, they suggested exactly that. It’s possible I don’t drink enough. Lately I have been doing more weights because of an injury that’s meant I can’t run. So I do strength training maybe 3 times a week. I know muscle mass can affect this too but I wouldn’t describe myself as muscly apart from on my legs, due to running (under normal circumstances) and martial arts.

In June, my eGFR (monitored because I am on blood pressure medication) came back at 66, whereas a year before it had been 75. I remember it was a very hot day (30 degrees plus), and a week before I had just finished a multi day hike, and I had been using ibuprofen gel on a niggly injury daily for weeks and weeks. I had a retest in November, before which I hadn't used ibuprofen for a couple of months, and I made sure I was well hydrated (2 litres of water each day for about a week leading up to it). My eGFR came back at 73. I do think exercise, medication and diet make quite a difference.

Thanks, I hope it’s something like that. Hard not to worry about it.

I’m in a similar situation. Had a set of blood tests done 2 years ago as was having heart palpitations, all came back normal except kidney function which was an eGFR of 58. They didn’t seem too worried about it, so I pretty much forgot about it, although I did think it was odd. The GP surgery got back in touch in November and said they wanted to repeat the test, which they did, and it’s still 58. They’ve therefore diagnosed me with stage 3 kidney disease. Apparently it’s usually associated with high blood pressure or diabetes, neither of which I have - my blood pressure, cholesterol, blood sugar and liver function are all well within normal range. I’m slightly overweight (BMI fluctuates between 26 and 27), but like the OP I also exercise 5-6 times a week, including lots of weight training, and I also eat quite a lot of protein, especially egg whites. I probably wasn’t drinking enough water so I’m now making a conscious effort to hydrate more, I’ve also cut back on salt and things like Diet Coke.

It’s all a bit of a mystery really. I’ve had recurrent bladder issues for over 20 years, so GP said it could be linked, but we’ll probably never know. They said I was an unusual case, but they don’t seem to be too worried so I’m trying not to be. I’ll have to have a blood test every 6 months to make sure my kidney function is stable, and im just trying to maintain a reasonably healthy diet and keep up my exercise routine (completely failed at this over Xmas though!) They wanted to put me on statins but I said no, as they calculated that my risk of a cardiovascular event is currently extremely low, plus I’m only 43 and don’t want to take something like that if I’m not convinced I need to.

I can’t say it’s not a bit worrying, but as my GP doesn’t seem too concerned I’m just trying to crack on, hopefully it’s also positive that my eGFR, while clearly lower than it should be, has remained stable for 2 years.

I only have one kidney, so have yearly kidney function tests. My consultant urologist always stresses the importance of being very well hydrated before the blood test.

Interesting. I too am borderline kidney disease and thought it was linked to my daily naproxen, which I take for arthritis. I've also had my gall bladder removed. Which I think might impact things?

I also do not drink enough water or fluids generally. I'll have 4 or 5 cups of tea and one large glass of water a day.

@Colinthedog that’s interesting … I definitely don’t have high blood pressure … in fact there have been times when I’ve been told it’s a bit low. I also don’t have diabetes (according to blood tests this week).

@Andthatrightsoon I’m trying to drink more water. Didn’t think I was that bad, but second guessing everything now.

@77Fee Naproxen can definitely affect kidney results as I was told this (but didn’t actually take the Naproxen that was prescribed for me).

What was the outcome op?

I'm currently having investigations on my kidneys because of out of range eGFR and creatinine. I'm on a lot of medication and was concerned this was the cause. My consultant wanted to know about my ibuprofen use, which I no longer take, but he was interested how much I'd used in the past. Aparently it can have a serious impact on your kidneys.

Thanks for asking. I’m actually still waiting for the second blood test, which is this coming week. So hopefully I will know more soon.

I did take a fair bit of ibuprofen in the months leading up to that first blood test due to various injuries, so I really hope it’s that.

@S0upertrooper I hope you also get answers soon.

eGFR calculation assumes you are an average 70kg man and so the results for women are somewhat skewed. Pop your results into this calculator that adjusts for age/ weight/ sex and see if the result is different (check you're using the correct units).

https://www.mdcalc.com/calc/43/creatinine-clearance-cockcroft-gault-equation

A one off result that is a bit low could be dehydration, diet, taking ibuprofen or certain supplements. Do you take any other meds / supplements (creatine?)?

I doubt you have anything to worry about. Exercise, eating a high protein meal, being dehydrated or being unwell can all increase your creatinine levels, which will in turn reduce your egfr (and the ‘r’ stands for estimated, as when kidney function is actually pretty ok - which a gfr of 60 or thereabouts still is - a small increase in creatinine can result in what seems like quite a big drop and is why doctors look at a trend). Taking creatine supplements or being muscular will also make your results inaccurate. You need to get retested a couple of times to understand the trend, when you’re well hydrated etc to see if there is actually a problem.

Even if there is, stage 3a isn’t too much to worry about. Follow a healthy diet, exercise, keep an eye on your blood pressure and control diabetes is you have it. You won’t need to follow any special diets etc - that only is needed in much later stages of kidney problems when your kidneys can no longer filter out potassium or phosphate, but if you google it you will often read that you should be on a kidney diet - please don’t make any of these changes unless a doctor says you actually need to! Only 2% of people with kidney disease ever need dialysis (and around 10% of the population has some form of kidney disease) so try not to worry!

Thanks for the helpful replies. Have had the second blood test now so I’ll see what happens with that.

I did try that calculator, thanks @AltitudeCheck . The eGFR came up as around 57.8, which is a bit higher than what it said on the NHS app. Not taking any supplements or anything but did take a fair bit of ibuprofen in the weeks leading up to that test.

fingers crossed it will be ok but your post is reassuring @happilypickled , thank you.

creatinine clearance (which is what that calculator is for) is not the same as eGFR or creatinine.

Hello! Kidney transplant patient here!

Hopefully your second test results come in and give you reassurance that it was a blip, however one part of your OP stood out to me - the weight training.

My kidney doctor once told me that a guy kept being referred to clinic with an egfr that would have normally suggested he was in renal failure. He wasn’t, he was just doing heavy weight training every day!

That amount of muscle exertion and being dehydrated could definitely lowered your result. As said by a PP, it’s always an estimate based on a few different factors, and any of those can throw it off.

Wishing you the best!

@MissKittyFantastico84 thank you for replying and I hope you’re doing well.

I really do hope it is a blip … they said I would “probably” get results today, so I’m feeling a bit nervous about it. And second guessing if there is a reason they have not popped up on the NHS app yet. I probably shouldn’t be looking!

I train with weights maybe 1-2 times a week and I think my legs are quite muscly, but my upper body is not. My training sessions are only 30 mins max at a time though and the weights are not super heavy, just 5kg or 6kg dumbbells depending on what I am doing.

I thought I would update this thread in case it helps anyone in the future, and also to say thanks to the people who replied.

I have finally got the results of the second blood test. Honestly I've been so worried about this that it's marred the first few weeks of 2026. The second result was normal. Creatinine was 76 umol/L, when previously it was 104 umol/L.

The eGFR was 79mL/min, which I understand is somewhat 'low', but there is a note on there saying that in the absence of other symptoms (I have no symptoms - I originally went to the GP for suspected gout and they did a whole suite of blood tests), this does not indicate abnormal kidney function. I'm pretty active, work out a lot, probably more muscle than fat.

I think the lesson here for me is don't take ibuprofen willy nilly when paracetamol will do.

So, finally, I can say I am not worried about this anymore. But thank you very much to all who replied and @S0upertrooper I hope you get reassuring news from your investigations. Also wishing you all the best @MissKittyFantastico84 .