Reading Blood Tests on Peritoneal Dialysis: What BUN 30, Creatinine 12.7, eGFR, Potassium 3.4 and TCO2 32 Mean, Which Values Need Fixing, and How to Eat Fruit and Vegetables Safely

From a peritoneal dialysis group: please tell me what each of these values means

Short answer: the overall picture is not worrying. The values to discuss with your doctor at the next visit are potassium 3.4 and TCO2 32, and the low BUN should be checked against albumin to make sure protein intake is adequate.

A member of a peritoneal dialysis group shared these results: BUN 30 mg/dL, creatinine 12.7 mg/dL, eGFR 4.25, sodium 139, potassium 3.4, chloride 95 and TCO2 32 mEq/L.
This article explains each value so you can discuss them with your doctor precisely. Reference ranges vary slightly between labs, and this does not replace the diagnosis of the doctor caring for you.

1. Waste markers: what BUN 30 and creatinine 12.7 tell you

Short answer: on dialysis, a low BUN is not always good and a high creatinine is not always bad. Both must be read alongside protein intake, muscle mass and albumin.

BUN 30: good clearance or low protein intake?

BUN comes from protein breakdown, and people on peritoneal dialysis lose protein into the fluid every day.
The KDOQI 2020 nutrition guideline
therefore suggests about 1.0–1.2 g of protein per kg of body weight per day for metabolically stable dialysis patients, more than for people with CKD not on dialysis.
BUN 30 may mean good clearance, but with low albumin, weight loss or poor appetite it may mean too little protein, which
a study of 140 CAPD patients (2009)
found often comes with low potassium, low albumin and more peritonitis.

Creatinine 12.7: it reflects muscle too, not just waste

Creatinine comes from muscle, so people with more muscle have higher values.
A study of 10,896 peritoneal dialysis patients (2013)
found that those with creatinine 12.0–13.9 had a lower risk of death than those at 8.0–9.9 (HR 0.71), while those below 4.0 had a higher risk (HR 1.36).
Creatinine of 12.7 on dialysis is therefore not a sign of poor dialysis, and you should not try to lower it by eating less or cutting meat on your own.

eGFR 4.25: does not apply on dialysis

The eGFR on your report is calculated automatically from creatinine using formulas built from people not on dialysis. Once you are on dialysis, creatinine is set by the dialysis fluid and your muscle, so this number does not tell you what percentage of your native kidneys is left.
Remaining kidney function is measured with a 24-hour urine collection, and it genuinely matters.
The CANUSA reanalysis (2001)
found each 5 L per week of residual kidney function lowered the risk of death by about 12%, whereas extra peritoneal clearance did not have the same effect.
Protecting residual function matters, for example by avoiding NSAID painkillers, dehydration and unnecessary contrast dye.

Value-by-value interpretation for peritoneal dialysis; reference ranges may vary by lab (shown as cards on mobile).

2. Potassium 3.4: why it runs low on peritoneal dialysis, and what it risks

Short answer: because the dialysis fluid contains no potassium and removes it every day, glucose in the fluid shifts potassium into cells, and intake often drops. A mildly low value is fixable, but it should not be left low.

Common causes

• Standard peritoneal dialysis fluid contains no potassium, so it removes potassium continuously all day
• Glucose in the fluid is absorbed and stimulates insulin, which shifts potassium into cells
• Low intake, poor appetite, or fruit and vegetable restrictions carried over too strictly from before dialysis
• Diarrhea, vomiting, laxatives or diuretics

Why it should not be ignored

A study of 266 peritoneal dialysis patients (2005)
found potassium below 3.5 in about 20%, and this group had a 1.79-fold higher risk of death, with potassium linked to nutritional status.
Data on 10,468 peritoneal dialysis patients (2012)
showed a U-shaped pattern: both potassium below 3.5 (HR 1.51) and 5.5 or higher (HR 1.52) carried a higher risk of death.
And a study of 140 CAPD patients
found peritonitis in 6.9% of those with low potassium versus 2.1% of those without, thought to be because a sluggish gut lets bacteria cross the bowel wall more easily.
These are observational studies, so they show associations; they do not prove that supplementing potassium removes the risk.

3. TCO2 32, chloride 95 and sodium 139: acid-base and fluid balance

Short answer: sodium is normal, while TCO2 32 is above target, meaning the blood leans slightly alkaline. Correcting potassium helps partly, but the doctor should also review medicines.

TCO2 is blood bicarbonate

Data on 121,351 dialysis patients (2013)
found people on peritoneal dialysis were much less likely to have low bicarbonate than those on hemodialysis, because the lactate buffer in the fluid is continuously converted to bicarbonate, and values below 22 were linked to higher mortality.
KDOQI 2020 suggests keeping it at 24–26 mmol/L, so 32 is above target. Common causes are the buffer in the fluid, low potassium, vomiting, or bicarbonate tablets and calcium-based phosphate binders.

If you take bicarbonate tablets, bring this result to your doctor and ask whether to reduce or stop them. Do not adjust them yourself.

Sodium 139 and fluid control

Sodium 139 is in the normal range and reflects the water-salt balance in the blood, but it does not tell you whether the body holds excess fluid. Fluid overload is judged by weight, blood pressure, swelling and the volume removed by dialysis.
The ISPD 2020 recommendations
advise judging dialysis by symptoms, fluid status, nutrition and quality of life together with the numbers, not by any single blood value.

4. Eating fruit and vegetables to raise potassium safely

Short answer: add gradually, choose fruit and vegetables before processed foods, recheck your blood, and never eat star fruit however low your potassium is.

Foods that help raise potassium, approximate level, how to eat them and cautions for people on peritoneal dialysis (shown as cards on mobile).

A review of 126 star fruit poisoning cases (2017)
found no deaths in people with normal kidney function, but 36% mortality in people with chronic kidney disease and 27% in people on dialysis. Hiccups were the most common first symptom, followed by confusion or seizures.

Comparison of ways to correct low potassium on peritoneal dialysis; generic and drug-class names only (shown as cards on mobile).

Frequently asked questions (FAQ)

Common questions about reading blood tests on peritoneal dialysis

Are BUN 30 and creatinine 12.7 good or bad on peritoneal dialysis?

Overall, not worrying. BUN 30 is fairly low for someone on dialysis and may mean good clearance or too little protein intake, which should be checked against blood albumin. Creatinine on dialysis also reflects muscle mass: a study of 10,896 peritoneal dialysis patients found those with creatinine 12.0–13.9 had about 29% lower risk of death than those at 8.0–9.9, so a high value does not necessarily mean poor dialysis.

Why do people on peritoneal dialysis often have low potassium?

Peritoneal dialysis fluid contains no potassium and removes it continuously every day, the glucose in the fluid stimulates insulin that shifts potassium into cells, and many patients eat little or restrict fruit and vegetables too strictly. A study of 266 patients found potassium below 3.5 in about 20%, linked to poorer nutrition. Other causes to check include diarrhea, vomiting, laxatives and diuretics.

Can the eGFR of 4.25 on my report go back up?

The eGFR the lab calculates automatically from creatinine cannot be used for people on dialysis, because blood creatinine is then set by dialysis and muscle mass, not only the native kidneys. Remaining kidney function is measured with a 24-hour urine collection, and it matters: the CANUSA reanalysis found each 5 L per week of residual function lowered the risk of death by about 12%. You can protect it by avoiding NSAID painkillers, dehydration and unnecessary contrast or medicines.

With low potassium, how should I eat fruit and vegetables?

Add moderate- to high-potassium fruit and vegetables gradually as your doctor or dietitian advises, such as banana, orange, guava, papaya and blanched leafy greens, then recheck blood at your next appointment. Choose fruit and vegetables before milk, nuts or processed foods, which are high in phosphorus. KDOQI 2020 advises adjusting dietary potassium to keep blood levels normal rather than restricting fruit and vegetables for everyone in the same way.

Can I buy potassium tablets or potassium salt and take them myself?

No. Potassium supplements need a doctor to set the dose and monitor blood levels, because too much can push potassium high enough to cause dangerous heart rhythms, especially with ACE inhibitors or ARBs or after a change in dialysis fluid. Potassium-based low-sodium salts or sauces should not be used as a self-supplement either.

What do TCO2 32 and chloride 95 mean?

TCO2 reflects blood bicarbonate. A value of 32 is above the 24–26 range suggested by KDOQI 2020, meaning the blood is slightly alkaline, and a chloride of 95, slightly low, goes with it. Common causes are the lactate buffer in dialysis fluid, low potassium, vomiting, or bicarbonate tablets and calcium-based phosphate binders. Correcting potassium may help partly, but the doctor may also need to review medicines.

Which fruit should people on dialysis never eat, even with low potassium?

Star fruit and star fruit juice, because they contain a nerve toxin the kidneys cannot clear. A review of 126 star fruit poisoning cases found 27% mortality among people on dialysis, with symptoms starting with hiccups and progressing to confusion or seizures. Also be careful with large amounts of fruit juice or coconut water, which add fluid, and herbal or concentrated juices of unknown potassium content.

Beyond this report, which other values should people on peritoneal dialysis check?

Albumin, phosphorus, calcium, parathyroid hormone, hemoglobin, daily urine volume, fluid removed by dialysis, and dialysis adequacy measures such as Kt/V. ISPD 2020 recommends judging dialysis by symptoms, fluid status, nutrition and quality of life together, not by any single blood value.

Scientific mechanism in brief

Summarized by Asst. Prof. Dr. Norawit Raatpiboon:
the peritoneum acts as a filtering membrane, and wastes and electrolytes diffuse from the blood into the fluid down their concentration gradients. Standard fluid contains no potassium, so the gradient persists all day and potassium is removed continuously. At the same time, glucose in the fluid is absorbed into the blood and stimulates insulin, which activates the sodium-potassium pump and moves potassium into cells, lowering blood levels further.
The lactate buffer in the fluid is converted by the liver into bicarbonate, which is why people on peritoneal dialysis often have higher bicarbonate than those on hemodialysis. When potassium is low, cells exchange potassium out for hydrogen in, pushing the blood further toward alkalosis.
Creatinine comes from the breakdown of creatine in muscle at a fairly constant rate, so once the kidneys stop working, its blood level reflects both dialysis and muscle mass. BUN depends on protein intake and protein breakdown, so it can fall both with good dialysis and with inadequate intake.

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