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Medical Associates  ·  Department of Nephrology ← Maintenance Hemodialysis module  ·  urinenephrology.org
Clinical Mastery Series  ·  Maintenance Hemodialysis

Ultrafiltration rate and treatment time

The arithmetic of UFR, the graded mortality signal, scaled versus absolute thresholds, the regulatory history, and time and frequency as the levers
Andrew Bland, MD, FACP, FAAP UICOMP · UDPA · Butler COM Reviewed September 2026 13 min read

Bottom line

Part of the Maintenance Hemodialysis mastery module. UFR = ultrafiltration rate, in mL/kg/h of post-dialysis weight unless stated; IDWG = interdialytic weight gain.

  • UFR risk is graded, not a cliff at 13. In 118,394 patients, mortality rose 3% per 1 mL/kg/h, with excess risk already detectable at 8 to under 10 mL/kg/h (HR 1.09) 1. Patients with heart failure showed risk at 10–13 mL/kg/h 2. 13 mL/kg/h is a ceiling, not a target.
  • Weight-scaling misleads at the extremes. At 13 mL/kg/h the mortality hazard was 1.20 for a 60-kg patient and more than 2.0 for a 100-kg patient; an absolute UFR above about 1,000 mL/h carried a hazard near 1.5 regardless of size (Raimann 2022) 3.
  • Every threshold is observational. No randomized trial has tested a UFR ceiling 1,4, and the 2015 KDOQI adequacy update gave no numeric ceiling 5.
  • CMS removed the UFR reporting measure from the ESRD Quality Incentive Program beginning payment year 2026 6. The measure only ever scored whether facilities reported the data needed to calculate UFR 7; its removal does not mean UFR stopped mattering.
  • Time is the lever. Each additional 30 minutes of session length was associated with 6–7% lower mortality in DOPPS 8,9. The only randomized test of longer sessions (TiME) separated its arms by 9 minutes, so it answers nothing 10.
  • More frequent sessions help surrogates and cost access. Six-times-weekly in-center dialysis lowered death or LV mass increase (HR 0.61) but raised access interventions (HR 1.71) 11, and frequent nocturnal dialysis accelerated loss of residual function 12.

1. The arithmetic

UFR is volume removed divided by time divided by body weight, expressed in mL/kg/h using post-dialysis weight. The CMS specification used exactly this: UFR = (weight change in kg × 1,000) ÷ (delivered minutes ÷ 60) ÷ post-dialysis weight 7.

UFR = UF volume (mL) ÷ session hours ÷ post-dialysis weight (kg)

Three things drive it: interdialytic weight gain, session length, and body size 13. Only two are in the unit’s hands.

Table 1. UFR (mL/kg/h) for a given UF volume and session length

Weight3 L in 3.5 h3 L in 4 h3 L in 4.5 h4 L in 3.5 h4 L in 4 h4 L in 4.5 h4 L in 5 h
60 kg14.312.511.119.016.714.813.3
70 kg12.210.79.516.314.312.711.4
80 kg10.79.48.314.312.511.110.0
100 kg8.67.56.711.410.08.98.0

Table 2. Maximum UF volume per session at a ceiling of 13 mL/kg/h (and at 10 mL/kg/h)

Post-HD weight3.5 h4 h4.5 h5 h13 mL/kg/h as mL/h
50 kg2.3 L (1.8)2.6 L (2.0)2.9 L (2.2)3.2 L (2.5)650
60 kg2.7 L (2.1)3.1 L (2.4)3.5 L (2.7)3.9 L (3.0)780
70 kg3.2 L (2.5)3.6 L (2.8)4.1 L (3.1)4.5 L (3.5)910
80 kg3.6 L (2.8)4.2 L (3.2)4.7 L (3.6)5.2 L (4.0)1,040
100 kg4.5 L (3.5)5.2 L (4.0)5.8 L (4.5)6.5 L (5.0)1,300
120 kg5.5 L (4.2)6.2 L (4.8)7.0 L (5.4)7.8 L (6.0)1,560

Worked example: removing 4 L from a 70-kg patient is 14.3 mL/kg/h over 4 hours, 11.4 over 5 hours, and 9.5 over 6 hours.

The last column matters for large patients

At 13 mL/kg/h, a 100-kg patient is ultrafiltered at 1,300 mL/h. Raimann and colleagues found the mortality hazard crossed 1.5 once absolute UFR exceeded 1,000 mL/h, largely independent of weight between 80 and 140 kg, and suggested approximately 900 mL/h as a warning level 3. For heavy patients, a weight-scaled ceiling of 13 is not conservative.

2. The observational evidence

No randomized trial has tested a UFR ceiling 1,4. Every number below is an association.

StudyPopulationKey result
Saran 2006 (DOPPS) 822,000 patients, 7 countriesUFR above 10 mL/kg/h: IDH OR 1.30; mortality RR 1.09. Sessions longer than 240 minutes: mortality RR 0.81; each 30 minutes longer RR 0.93
Movilli 2007 14287 Italian patients, 5 yearsEach unit of UFR: HR 1.22 (1.16–1.28); best survival below 12.37 mL/kg/h
Flythe 2011 (HEMO) 21,846 patientsAbove 13 vs 10 or below: all-cause HR 1.59, cardiovascular HR 1.71. 10–13 associated with death only in heart failure. Risk begins to rise above 10
Assimon 2016 1118,394 patients, 2008–2012Above 13 vs 13 or below: HR 1.31 (1.28–1.34). Above 10 vs 10 or below: HR 1.22 (1.20–1.24). 3% higher risk per 1 mL/kg/h; versus below 6: 8–<10 HR 1.09, 10–<12 HR 1.15, 12–<14 HR 1.23, 14 or more HR 1.43
Raimann 2022 32,542 incident patientsHazard at 13 mL/kg/h depends on size: 1.20 (60 kg), 1.45 (80 kg), above 2.0 (100 kg). Unscaled above 1,000 mL/h: HR 1.5

KDIGO 2020 summarizes it: higher UF rates, even as low as 6 mL/kg/h, are associated with higher mortality, and a single threshold for all patients at all times is likely inappropriate 4.

Why rate would matter

Ultrafiltration removes fluid from plasma, and plasma refills from the interstitium at a finite rate. When removal outruns refill, effective circulating volume falls despite total-body overload.

  • Myocardial stunning. In 70 prevalent patients, 64% developed dialysis-induced regional wall-motion abnormalities; UF volume, intradialytic hypotension, age, and troponin T were independent determinants, and stunning was associated with 12-month mortality and lower ejection fraction in survivors 15. PET imaging linked these abnormalities to a fall of more than 30% in segmental myocardial blood flow 16.
  • Frequency reduces stunning. More frequent regimens with lower UF volumes and rates had fewer wall-motion abnormalities per patient, with nocturnal home hemodialysis the lowest 17.

3. Is the threshold scaled or unscaled?

The field adopted mL/kg/h because the early studies scaled to weight 2,8,14. Two analyses push in opposite directions. Assimon found weight-normalized UFR had the strongest association with mortality among the normalizations tested, with the association stronger in heavier patients 1. Raimann found that the risk at a fixed mL/kg/h rises with body size, so a weight-scaled threshold permits dangerous absolute rates in large patients and is overly strict in small ones 3.

Both are compatible with one practical rule: use mL/kg/h as the everyday ceiling, and add an absolute cap near 900–1,000 mL/h for patients above approximately 80 kg 3. That cap is a judgment call; no trial has tested it.

4. Guidelines and regulators

KDOQI and the NKF controversies report

The 2015 KDOQI Hemodialysis Adequacy update 5 recommends a minimum of 3 hours per session for patients with low residual kidney function on thrice-weekly dialysis; suggests considering additional sessions or longer treatment times for large weight gains, high UF rates, poorly controlled blood pressure, difficulty achieving dry weight, or poor metabolic control; recommends reducing dietary sodium and achieving adequate sodium and water removal to manage hypertension, hypervolemia, and LV hypertrophy; and advises prescribing a UF rate that balances euvolemia, blood-pressure control, and solute clearance against hemodynamic instability. It gave no numeric UFR ceiling 5.

The 2016 NKF-KDOQI Controversies Report laid out the benefits and pitfalls of using any UFR threshold as a performance measure, after the National Quality Forum endorsed a measure of UFR of 13 mL/kg/h or more in sessions shorter than 240 minutes 13.

What facilities would have had to do. Using 2012 dialysis-organization data, 15.8%–22.8% of a facility’s patients exceeded 13 mL/kg/h depending on the definition, and a facility of more than 100 patients would need approximately 33 extra treatment-hours a week to bring every patient under 13 with sessions capped at 4 hours 18. Capping UFR at 13 without extending time or reducing IDWG would add a theoretical 1.4 ± 3.0 kg of fluid per patient per month 19.

The CMS measure: history

RuleAction
CY 2017 ESRD PPS Final RuleUltrafiltration Rate reporting measure adopted for payment year 2020. It scored the percentage of patient-months for which the facility reported the data elements needed to calculate UFR (pre- and post-weight, delivered minutes, sessions). It was not scored against 13 mL/kg/h 7
CY 2024 ESRD PPS Final Rule (fact sheet, October 2023)Measure removed beginning payment year 2026 under the removal factor for measures whose performance does not result in better or intended patient outcomes, because documenting UFR may not indicate the quality of care 6
Two common misstatements

“CMS uses UFR above 13 mL/kg/h as a quality measure” is wrong: the QIP measure was a reporting measure, and it has been removed beginning payment year 2026 6,7. And the removal does not mean UFR is unimportant: CMS removed a data-completeness measure, while the observational mortality gradient is unchanged 1,2,3.

UK guidance

The 2019 UK Renal Association guideline recommends avoiding excessive UF rates by addressing fluid gains, accepting staged achievement of target weight, or using an augmented schedule, with no numeric maximum in the adult recommendation. Its rationale text cites the DOPPS threshold of 10 mL/kg/h and the HEMO threshold of 13 mL/kg/h, and warns that avoiding high rates should not come at the expense of failing to reach target weight and accepting over-hydration 20.

5. Treatment time and frequency

When the UF requirement exceeds what the ceiling allows, there are three moves: remove the fluid over more time, bring less fluid in, or accept leaving some behind. KDIGO lists the same levers: lengthen or add treatments, reduce IDWG, and improve vascular tolerance 4.

Longer sessions

  • DOPPS 2006 (observational): sessions longer than 240 minutes, RR 0.81 for death; each additional 30 minutes, RR 0.93 8.
  • DOPPS 2012 (observational, 37,414 patients): per 30 minutes longer, all-cause mortality HR 0.94 (0.92–0.97), cardiovascular HR 0.95, sudden death HR 0.93, with lower pre- and post-dialysis systolic pressure and lower phosphorus 9.
  • TiME (cluster RCT, 7,035 incident patients, 266 units, default of 255 minutes or more): stopped at a median 1.1 years because the arms barely separated, 216 versus 207 minutes, with no difference in mortality or hospitalization 10.

Appraisal (TiME). A 9-minute difference cannot test the hypothesis. TiME is a lesson in pragmatic-trial implementation, not evidence that longer sessions do not help. The observational association remains the best available evidence, with the caveat that patients who stay longer may be healthier or more adherent. In practice, adding 30 minutes turns 4 L in 4 hours for a 70-kg patient from 14.3 to 12.7 mL/kg/h; adding an hour gets to 11.4 (Table 1).

More frequent sessions

TrialDesignResult
FHN Daily 11RCT, 245 patients, 6 vs 3 in-center sessions per week, 12 monthsDeath or LV mass increase: HR 0.61 (0.46–0.82). Death or worse physical health: HR 0.70 (0.53–0.92). Better BP and phosphorus control. Access interventions HR 1.71 (1.08–2.73)
FHN Daily long-term follow-up 21Same cohort, median 3.6 yearsDeaths 16% vs 28%; HR 0.54 (0.31–0.93)
FHN access analysis 22Both FHN trialsFirst access event HR 1.76 (1.11–2.79); AV access HR 1.90
FHN Nocturnal 23RCT, 87 patients, 6 nights vs 3 sessions per weekNeither coprimary composite significant (HR 0.68 and 0.91); better BP and phosphorus
FHN residual function 12Nocturnal trial, 63 with residual functionUrine output fell to zero in 52% vs 18% (4 months) and 67% vs 36% (12 months)
Alberta nocturnal 24RCT, 52 patients, 6 monthsLV mass −15.3 g; fewer antihypertensives (16/26 vs 3/25)

Appraisal (FHN Daily). The coprimary outcomes are composites driven by LV mass, a surrogate. The long-term mortality difference (absolute 12 percentage points; approximately 8 patients treated for one year per death avoided over 3.6 years) comes from post-trial follow-up of a 12-month intervention and was not the primary endpoint: hypothesis-supporting, not definitive. The harms are concrete: more access repairs 22 and, with nocturnal therapy, faster loss of residual function 12.

Extend today, add a session, or isolated ultrafiltration?

OptionWhen it fitsTrade-offs
Extend today’s sessionA single large gain; UFR would exceed the ceilingChair time and patient preference 4; adds solute clearance too 9
Add a full sessionRecurrent large gains, the long interval, concurrent hyperkalemia or poor clearanceAccess use 22; logistics
Isolated (sequential) UFVolume is the only problem; potassium and clearance are controlledRemoves fluid without solute clearance; KDIGO rates it as limited evidence that concentrates removal into a time-limited high-rate period 4
Reset target upward temporarilyAcute illness, severe symptomsAcceptable short term; weigh the long-term cost of overload 4
Calculate today’s UFR from the UF goal, scheduled hours, and post-dialysis weight
Above the ceiling (13 mL/kg/h, or roughly 1,000 mL/h in a large patient)?
↓ if yes
Single large gain
Extend today’s session; it adds clearance too
Recurrent large gains
Add a session or lengthen the schedule; address sodium intake and IDWG
Acute illness or severe symptoms
Accept a temporarily higher target; weigh the cost of overload
Volume the only problem
Isolated UF is an option, with limited evidence
Figure 1. When the ultrafiltration goal will not fit in the scheduled time. Options from KDIGO 2020 and the observational time data 3,4,9; an expert synthesis, not a tested algorithm.

Claims that sequential UF reduces intradialytic hypotension by 20–40% have no identifiable source, and pairing it with sodium profiling is not supported: routine sodium profiling was associated with higher all-cause and cardiovascular mortality in DOPPS facility data (HR 1.36 and 1.34) 25.

The long interdialytic interval

Across 32,065 US patients, the day after the 2-day gap carried higher all-cause mortality (22.1 vs 18.0 per 100 person-years), cardiac mortality, and admissions for heart failure (29.9 vs 16.9) and arrhythmia (20.9 vs 11.0) 26. The first session of the week is the one where the UF requirement peaks, and it is the session to extend.

Interdialytic weight gain and sodium

Less fluid in means less fluid out. A 2024 meta-analysis (8 studies, 783 patients) found that low-salt diets or salt-focused counseling reduced the odds of IDWG above 2.5 kg (OR 0.57, 0.33–0.97) 27. Each 1 mEq/L higher facility dialysate sodium was associated with 0.13% higher relative IDWG in DOPPS 28 (see Dialysate sodium). KDOQI 2015 recommends reducing dietary sodium alongside adequate removal on dialysis 5, and in patients with residual function, diuretics increase urine output and reduce the UF requirement 4.

Evidence gaps

  • No RCT has tested a UFR ceiling. Every threshold (10, 13, 900–1,000 mL/h) rests on observational data with residual confounding by body size, heart failure, and adherence 1,3,13.
  • Longer sessions have never been adequately tested; TiME separated its arms by 9 minutes 10.
  • The absolute cap of approximately 900–1,000 mL/h for large patients is derived from one cohort and untested as a rule 3.
  • Frequent dialysis mortality benefit rests on post-trial follow-up rather than a primary endpoint 21.
  • Isolated ultrafiltration is supported only by limited evidence, and it concentrates removal into a time-limited high-rate period 4.

At the chair

For dialysis nurses and technicians

Calculate the UFR before starting: UF volume in mL, divided by session hours, divided by post-dialysis weight. Treat 13 mL/kg/h as a ceiling to stay under, not a number to reach, and for heavier patients check the absolute rate against roughly 1,000 mL/h. When the goal will not fit in the scheduled time, time is the lever: report it so the session can be extended or a treatment added rather than the rate pushed up. The first session after the long weekend is the one most likely to need more time.

Nursing card N4: UF rate table: when to extend or add time

The physician’s written order and the unit protocol always govern.

Also in this module

References

References are carried from a reference-checked evidence review (September 2026) and renumbered for this page. Each was checked against its PubMed record, full text, or the issuing agency’s document.

  1. Assimon MM, Wenger JB, Wang L, Flythe JE. Ultrafiltration rate and mortality in maintenance hemodialysis patients. Am J Kidney Dis. 2016;68(6):911-922. PMID: 27575009
  2. Flythe JE, Kimmel SE, Brunelli SM. Rapid fluid removal during dialysis is associated with cardiovascular morbidity and mortality. Kidney Int. 2011;79(2):250-7. PMID: 20927040
  3. Raimann JG, Wang Y, Mermelstein A, Kotanko P, Daugirdas JT. Ultrafiltration rate thresholds associated with increased mortality risk in hemodialysis, unscaled or scaled to body size. Kidney Int Rep. 2022;7(7):1585-1593. PMID: 35812299
  4. Flythe JE, Chang TI, Gallagher MP, et al. Blood pressure and volume management in dialysis: conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference. Kidney Int. 2020;97(5):861-876. PMID: 32278617
  5. National Kidney Foundation. KDOQI Clinical Practice Guideline for Hemodialysis Adequacy: 2015 update. Am J Kidney Dis. 2015;66(5):884-930. PMID: 26498416
  6. Centers for Medicare & Medicaid Services. Calendar Year 2024 End-Stage Renal Disease (ESRD) Prospective Payment System (PPS) Final Rule (CMS-1782-F) — fact sheet, October 27, 2023. Not PubMed-indexed.
  7. Centers for Medicare & Medicaid Services. ESRD Quality Incentive Program: Payment Year 2020 Final Measure Technical Specifications — Ultrafiltration Reporting Measure (governing rule: CY 2017 ESRD PPS Final Rule). Not PubMed-indexed.
  8. Saran R, Bragg-Gresham JL, Levin NW, et al. Longer treatment time and slower ultrafiltration in hemodialysis: associations with reduced mortality in the DOPPS. Kidney Int. 2006;69(7):1222-8. PMID: 16609686
  9. Tentori F, Zhang J, Li Y, et al. Longer dialysis session length is associated with better intermediate outcomes and survival among patients on in-center three times per week hemodialysis: results from the Dialysis Outcomes and Practice Patterns Study (DOPPS). Nephrol Dial Transplant. 2012;27(11):4180-8. PMID: 22431708
  10. Dember LM, Lacson E Jr, Brunelli SM, et al. The TiME Trial: a fully embedded, cluster-randomized, pragmatic trial of hemodialysis session duration. J Am Soc Nephrol. 2019;30(5):890-903. PMID: 31000566
  11. FHN Trial Group; Chertow GM, Levin NW, Beck GJ, et al. In-center hemodialysis six times per week versus three times per week. N Engl J Med. 2010;363(24):2287-300. PMID: 21091062
  12. Daugirdas JT, Greene T, Rocco MV, et al. Effect of frequent hemodialysis on residual kidney function. Kidney Int. 2013;83(5):949-58. PMID: 23344474
  13. Kramer H, Yee J, Weiner DE, et al. Ultrafiltration rate thresholds in maintenance hemodialysis: an NKF-KDOQI Controversies Report. Am J Kidney Dis. 2016;68(4):522-532. PMID: 27449697
  14. Movilli E, Gaggia P, Zubani R, et al. Association between high ultrafiltration rates and mortality in uraemic patients on regular haemodialysis: a 5-year prospective observational multicentre study. Nephrol Dial Transplant. 2007;22(12):3547-52. PMID: 17890254
  15. Burton JO, Jefferies HJ, Selby NM, McIntyre CW. Hemodialysis-induced cardiac injury: determinants and associated outcomes. Clin J Am Soc Nephrol. 2009;4(5):914-20. PMID: 19357245
  16. McIntyre CW, Burton JO, Selby NM, et al. Hemodialysis-induced cardiac dysfunction is associated with an acute reduction in global and segmental myocardial blood flow. Clin J Am Soc Nephrol. 2008;3(1):19-26. PMID: 18003765
  17. Jefferies HJ, Virk B, Schiller B, Moran J, McIntyre CW. Frequent hemodialysis schedules are associated with reduced levels of dialysis-induced cardiac injury (myocardial stunning). Clin J Am Soc Nephrol. 2011;6(6):1326-32. PMID: 21597028
  18. Flythe JE, Assimon MM, Wenger JB, Wang L. Ultrafiltration rates and the Quality Incentive Program: proposed measure definitions and their potential dialysis facility implications. Clin J Am Soc Nephrol. 2016;11(8):1422-1433. PMID: 27335126
  19. Flythe JE, Assimon MM, Overman RA. Target weight achievement and ultrafiltration rate thresholds: potential patient implications. BMC Nephrol. 2017;18(1):185. PMID: 28578687
  20. Ashby D, Borman N, Burton J, et al. Renal Association Clinical Practice Guideline on Haemodialysis. BMC Nephrol. 2019;20(1):379. PMID: 31623578
  21. Chertow GM, Levin NW, Beck GJ, et al. Long-term effects of frequent in-center hemodialysis. J Am Soc Nephrol. 2016;27(6):1830-6. PMID: 26467779
  22. Suri RS, Larive B, Sherer S, et al. Risk of vascular access complications with frequent hemodialysis. J Am Soc Nephrol. 2013;24(3):498-505. PMID: 23393319
  23. Rocco MV, Lockridge RS Jr, Beck GJ, et al. The effects of frequent nocturnal home hemodialysis: the Frequent Hemodialysis Network Nocturnal Trial. Kidney Int. 2011;80(10):1080-91. PMID: 21775973
  24. Culleton BF, Walsh M, Klarenbach SW, et al. Effect of frequent nocturnal hemodialysis vs conventional hemodialysis on left ventricular mass and quality of life: a randomized controlled trial. JAMA. 2007;298(11):1291-9. PMID: 17878421
  25. Dasgupta I, Thomas GN, Clarke J, et al. Associations between hemodialysis facility practices to manage fluid volume and intradialytic hypotension and patient outcomes. Clin J Am Soc Nephrol. 2019;14(3):385-393. PMID: 30723164
  26. Foley RN, Gilbertson DT, Murray T, Collins AJ. Long interdialytic interval and mortality among patients receiving hemodialysis. N Engl J Med. 2011;365(12):1099-107. PMID: 21992122
  27. Bossola M, Mariani I, Antocicco M, et al. Interdialytic weight gain and low-salt diet in patients on chronic hemodialysis: a systematic review and meta-analysis. Clin Nutr ESPEN. 2024;63:105-112. PMID: 38941185
  28. Wong MM, McCullough KP, Bieber BA, et al. Interdialytic weight gain: trends, predictors, and associated outcomes in the international Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis. 2017;69(3):367-379. PMID: 27866963