Lactic acid, lactate in ME/CFS

I'm not sure where the lactic acid is supposed to be. I don't think there is good evidence for increased levels of lactic acid in the blood of people with ME/CFS, or for abnormal responses to exercise in terms of lactic acid?

I know there was that n=1 paper by Vink, but I think members' experimentation with lactic acid monitors, including my own, didn't find that issues with lactic acid were a common problem.
 
Hutan said:
I'm not sure where the lactic acid is supposed to be. I don't think there is good evidence for increased levels of lactic acid in the blood of people with ME/CFS, or for abnormal responses to exercise in terms of lactic acid?

I know there was that n=1 paper by Vink, but I think members' experimentation with lactic acid monitors, including my own, didn't find that issues with lactic acid were a common problem.
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For what it's worth, in the PEM conference the other day, I believe three different groups (Putrino, Puta and another one) showed either preliminary or clinical data from their clinics - all of them seeing increased plasma lactate during rest and activity compared to healthy adults. It was explained with dysfunctional TCA / increased anaerobic glycolysis iirc (pyruvate -> lactate -> exported lactate). I don't remember them trying to explain that this increased lactate is anything else but an outcome of the former - I don't think they made lactate more than a potential diagnostic marker. Not a main driver of disease state I think. Not 100% certain I remember correctly.
 
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My lactate was 1 decimal point below the top end of normal when first seen in the emergency dept. Really, that was quite abnormal for a supposedly fit and healthy 50yo (at the time). I was doing nothing and the normal range encompasses the full adult age and fitness range.

@Kiwipom I wonder if you might have a comment on your experience with looking at lactate.
 
Adding this n=2 data from a reddit post today here, noting elevated lactate readings after a long delay. Someone who classifies themselves as very severe and another responding.

Lactate levels 24 hours after an appointment at which I was told I'm just deconditioned and need to exercise. FML
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The reading in the submitted image is 7.2 mmol/L

For context, the 'exertion' involved in this was being taken into hospital on a stretcher in an ambulance, lying down for the entirety of the appointment, and then being taken home and not being able to get out of bed since.

Interestingly, my lactate levels were only somewhat elevated (2.4 mmol/l) immediately after the appointment. This huge increase seems to have come later, i.e. some time after the actual activity itself.
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A reply from someone who classifies themselves as suspected/undiagnosed —

I once did a test where i had to sit down and stand back up for 3 minutes at the pneumologists, with the point being to text my blood oxygenation. My oxygenation was perfectly fine but my lactate went from 1,2 mmol/l to 8,0 mmol/l in these 3 min- No one gave a single fuck about this, while it felt like a very clear "this could be something" moment for me. Since i dont have any other clue as to whats going on with me and why im in so much pain during and after any exhaustion.
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My lactate was below 1mmol/l only twice, and both times after a shower, 1000 mg ibuprofen and much rest.
It was always way above 1mmol/l the other days. I didnt ever exercise or do anything straining and yet it was always above 2 mmol/l in the morning and on average 3-4mmol/l in the evening. And after exhaustion i noticed 4-5mmol/l HOURS afterwards (example exhaustion at 10am, measuring at 3pm).
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For reference and informational purposes.

1) During a recent immune treatment of a month my lactate was measured regularly (using a catheter) in the morning waking up at rest and I stayed inpatient. So literally zero activity.

Lactate (09.09.25) – 9.0 mmol/l (range 0.5 – 1.6)
Lactate (16.09.25) – 3.6 mmol/l (range 0.5 – 1.6)
Lactate (18.09.25) – 3.4 mmol/l (range 0.5 – 1.6)
Lactate (22.09.25) – 2.6 mmol/l (range 0.5 – 1.6)
Lactate (25.09.25) – 3.1 mmol/l (range 0.5 – 1.6)
Lactate (30.09.25) – 3.8 mmol/l (range 0.5 – 1.6)
Lactate (06.10.25) – 2.7 mmol/l (range 0.5 – 1.6)

2) as you can see my values started very high and slowly went down
And this corresponds with improvement of all symptoms, most importantly, OI and PEM.
- Also burning muscles feeling (and poisonous feeling) diminished while I was exerting much more every day.
So for me there’s a direct correlation with symptoms/severity and lactate levels
Unfortunately I have relapsed since then

3) as far as I can asses now I think the temporary improvements were caused by high dosage Dexamethasone (and many IV fluids)

4) I think levels are a downstream effect - but for me - and probably for a subgroup - it’s an important marker of our severity and pain levels
- I have continuous burning muscles, specially my arms, with the least exertion
 
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There seems to be something amiss with all the evidence gathered here. Reference sources indicate that a lactate above 2 mmol/L is abnormal and above 4 seriously so, to the extent of suggesting sepsis or metabolic failure. People are reporting very high values without any apparent evidence of extreme exercise, sepsis or organ failure.

My memory is that lactate levels used to be done on samples kept on ice and transported rapidly to the lab. Presumably without careful handling you can get artifactual high levels. I wonder if this is an issue. Lactate as a basis for PEM symptoms makes no sense to me at all - for reasons given by others.
 
Perhaps a circulation problem? If blood flow to the muscles is impaired, the muscle cells are less able to utilize oxygen and switch earlier to anaerobic metabolism, which produces lactate.

There was a thread about abnormal blood lactate after exercise:

Kalliope said:
Physiological Reports Abnormal blood lactate accumulation during repeated exercise testing in myalgic encephalomyelitis/chronic fatigue syndrome by Katarina Lien et al

Abstract
Post‐exertional malaise and delayed recovery are hallmark symptoms of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Studies on repeated cardiopulmonary exercise testing (CPET) show that previous exercise negatively affects oxygen uptake (VO2) and power output (PO) in ME/CFS. Whether this affects arterial lactate concentrations ([Laa]) is unknown.

We studied 18 female patients (18–50 years) fulfilling the Canadian Consensus Criteria for ME/CFS and 15 healthy females (18–50 years) who underwent repeated CPETs 24 h apart (CPET1 and CPET2) with [Laa] measured every 30th second. VO2 at peak exercise (VO2peak) was lower in patients than in controls on CPET1 (P < 0.001) and decreased in patients on CPET2 (P < 0.001).

However, the difference in VO2peak between CPETs did not differ significantly between groups. [Laa] per PO was higher in patients during both CPETs (Pinteraction < 0.001), but increased in patients and decreased in controls from CPET1 to CPET2 (Pinteraction < 0.001).

Patients had lower VO2 (P = 0.02) and PO (P = 0.002) at the gas exchange threshold (GET, the point where CO2production increases relative to VO2), but relative intensity (%VO2peak) and [Laa] at GET did not differ significantly from controls on CPET1. Patients had a reduction in VO2 (P = 0.02) and PO (P = 0.01) at GET on CPET2, but no significant differences in %VO2peak and [Laa] at GET between CPETs.

Controls had no significant differences in VO2, PO or %VO2peak at GET between CPETs, but [Laa] at GET was reduced on CPET2 (P = 0.008).

In conclusion, previous exercise deteriorates physical performance and increases [Laa] during exercise in patients with ME/CFS while it lowers [Laa] in healthy subjects.
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Jonathan Edwards said:
There seems to be something amiss with all the evidence gathered here. Reference sources indicate that a lactate above 2 mmol/L is abnormal and above 4 seriously so, to the extent of suggesting sepsis or metabolic failure. People are reporting very high values without any apparent evidence of extreme exercise, sepsis or organ failure.

My memory is that lactate levels used to be done on samples kept on ice and transported rapidly to the lab. Presumably without careful handling you can get artifactual high levels. I wonder if this is an issue. Lactate as a basis for PEM symptoms makes no sense to me at all - for reasons given by others.
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Maybe I’m an anomaly, but I doubt it, as I’ve spoken to a few more patients with exact similar symptomalogy.
(But not as extensive testing because that’s just very rare)

These measurements were taken in an academic hospital early in the morning before even getting out of bed. Immediately brought to the hospital lab. Seeing the first result of measurement my doctor was puzzled and shocked by the high lactate level and said exactly the same thing as you: this level would suggest sepsis.

I’m talking about this one : 9 of September 2025.
(And I would expect it to be even higher in the course of the day as burning-muscle symptoms and exertion increase)
Lactate (09.09.25) – 9.0 mmol/l (range 0.5 – 1.6)
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PS: I’ve taken an interest into lactate levels already since 2017 when my first measurement was high (corresponding with a crash)
Consecutive measurements have been increasingly higher corresponding with my worsening (currently bedbound)
 
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