# N1 — Potassium Bath Selection

N1 — Potassium Bath Selection FRONT Front · at the chair

**When:** pre-dialysis labs are back.

### Do this

1.  Compare today’s potassium (K) with the last 2–3 values and the current bath.
2.  Check the sample: hemolyzed, drawn late, or an unexpected jump? Request confirmation through the clinical pathway when the result is unexpected; do not delay urgent assessment or treatment for severe hyperkalemia, symptoms, or ECG changes while awaiting a repeat.
3.  Use the **7-to-8 rule**: pre-dialysis K + bath K = 7 to 8, using **2K or 3K**. Use this local rule only within the signed order or an authorized protocol; arithmetic alone does not authorize a bath change. Keep a prescribed bath that is working.

| Pre-dialysis K (mEq/L) | Usual bath | Nursing action |
|----|----|----|
| Below 3.5 | 3K | Call |
| 3.5–5.0 | 3K | None |
| 5.1–5.5 | 3K (2K if recurrent) | Note the trend |
| 5.6–5.9 | 2K | Note the trend |
| 6.0–6.4, no symptoms, no ECG change | 2K | Repeat pre-dialysis K at the next treatment — **call the nephrologist instead if the patient missed a treatment, takes digoxin, or has atrial fibrillation** |
| 6.5 or higher, or symptoms, or ECG change | Per nephrologist | **Call now** — see [N12: Chair-Side Emergencies](https://urinenephrology.org/mastery/maintenance-hd/nursing/N12-Chair-Side-Emergencies.html) |

1.  Atrial fibrillation, heart disease, or digoxin: favor the higher bath of the pair (sum of 8; 3K over 2K) unless ordered otherwise \[[3](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-3)\].
2.  If the bath changes for one value, document the reason, the recheck date, and the plan to return to the usual bath.

### Call the nephrologist when

- K is 6.5 or higher — before starting treatment.
- K is 6.0–6.4 and the patient missed a treatment, takes digoxin, or has atrial fibrillation (per unit protocol).
- Any K with weakness, palpitations, fainting, a slow pulse, or ECG change.
- K is below 3.5.
- An order calls for a bath below 2K or above 3K.
- It is the first treatment after a hospital stay.
- At rounds: a repeat pre-dialysis K is again 6.0 or higher (review diet, bowels, medicines, binder, treatment time).

### Don’t

- Don’t use 0K or 1K, or 4K, without a specific order and a monitoring plan \[[1](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-1)\].
- Don’t lower the bath for a single 5.5 in a patient who is usually controlled.
- Don’t leave a temporary bath change in place until next month’s labs.
- Don’t give potassium based on a value drawn right after dialysis \[[4](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-4)\].

N1 — Potassium Bath Selection BACK Back · why, and the evidence

### Why

1.  Patients who arrested in the dialysis unit were nearly twice as likely to have been on a 0K or 1K bath that day (17.1% vs 8.8%) \[[1](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-1)\].
2.  In 55,183 patients across 20 countries, 3K and 2K carried the same risk of death (HR 0.96) \[[2](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-2)\]; in older patients, 3K had 13% fewer new atrial fibrillation diagnoses than 2K \[[3](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-3)\].
3.  Changing the bath by 1 mEq/L moves the next pre-dialysis K by less than 0.1 mEq/L \[[2](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-2)\]. Diet, bowels, medicines, and binders move it more.
4.  After dialysis, potassium climbs back: about 35% of the drop returns within 1 hour and about 70% by 6 hours \[[4](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-4)\].
5.  Cardiac-arrest deaths and arrhythmia admissions cluster after the long weekend gap \[[5](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html#n1-ref-5)\].

### Go deeper

- Mastery page: [Dialysate potassium: bath selection and the rule of 7 vs 8](https://urinenephrology.org/mastery/maintenance-hd/dialysate-potassium-bath-selection.html)
- [All dialysis nursing reference cards](https://urinenephrology.org/mastery/maintenance-hd/nursing/index.html)

### References

1.  Karnik JA, et al. Cardiac arrest and sudden death in dialysis units. *Kidney Int.* 2001;60:350-357. [PubMed 11422771](https://pubmed.ncbi.nlm.nih.gov/11422771/)
2.  Karaboyas A, et al. Dialysate potassium, serum potassium, mortality, and arrhythmia events in hemodialysis (DOPPS). *Am J Kidney Dis.* 2017;69:266-277. [PubMed 27866964](https://pubmed.ncbi.nlm.nih.gov/27866964/)
3.  Hu A, et al. Serum and dialysate potassium and incident atrial fibrillation in older US persons initiating hemodialysis. *Kidney Int Rep.* 2023;8:305-316. [PubMed 36815107](https://pubmed.ncbi.nlm.nih.gov/36815107/)
4.  Ahmed J, Weisberg LS. Hyperkalemia in dialysis patients. *Semin Dial.* 2001;14:348-356. [PubMed 11679104](https://pubmed.ncbi.nlm.nih.gov/11679104/)
5.  Foley RN, et al. Long interdialytic interval and mortality among patients receiving hemodialysis. *N Engl J Med.* 2011;365:1099-1107. [PubMed 21992122](https://pubmed.ncbi.nlm.nih.gov/21992122/)

Reviewed by Andrew Bland, MD, FACP, FAAP · v1.0 draft 2026-09-26. For education; the physician’s written order and the unit protocol always govern.


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[Website version](https://urinenephrology.org/mastery/maintenance-hd/nursing/N1-Potassium-Bath-Selection.html) · Markdown synchronized October 3, 2026.