Clinician Guides 7 min read·Updated 16 July 2026 Clinician-reviewed

eGFR Blood Test Results Explained

A UK Consultant Nephrologist-led plain-English guide to your eGFR number — what it means, what affects it, and how diet and evidence-based supplements fit in.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 16 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

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Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

eGFR estimates kidney filtering capacity from a blood creatinine test. Normal is ≥90. Stages 3a–3b (30–59) are moderate CKD; under 15 is kidney failure. A single low result should be repeated. Creatine supplements and dehydration can artificially lower eGFR.

Key recommendation: eGFR is an estimate, not a direct measurement.

Quick answer

✓ Best choices

  • Vegetables, lower-potassium fruit and whole grains
  • Sensible portions of fish, eggs, chicken or tofu
  • Olive oil and unsalted nuts in small amounts

✓ Foods to limit

  • Added salt and ultra-processed foods
  • Phosphate additives in processed meats and ready meals
  • Sugary and energy drinks

Key takeaway

eGFR estimates kidney filtering capacity from a blood creatinine test. Normal is ≥90. Stages 3a–3b (30–59) are moderate CKD; under 15 is kidney failure. A single low result should be repeated. Creatine supplements and dehydration can artificially lower eGFR.

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Why this matters in chronic kidney disease

In chronic kidney disease (CKD), the kidneys gradually lose their ability to filter waste, balance electrolytes and clear excess nutrients. That means substances which are completely safe at typical doses in a healthy adult — including some vitamins and minerals — can build up or place added strain on the kidneys as function declines.

That's why UK renal nutrition guidance from NICE (NG203), KDOQI 2020 and the British Dietetic Association Renal Nutrition Group all take a cautious, individualised view of supplementation in CKD. The aim is to support overall nutrition without adding to the kidneys' workload.

Putting this into practice

If you're choosing a daily supplement and you have reduced kidney function, the most practical checks are simple: read the label, look at the doses, and look for what isn't added. Renal teams typically flag high-dose vitamin A (retinol), large doses of vitamin C, and any added potassium, phosphate or magnesium — these are the four ingredients most often singled out in routine dietetic reviews.

A evidence-based daily supplement keeps doses moderate, names the things it deliberately leaves out, and is formulated with renal nutrition in mind from the start — not adapted after the fact.

What to discuss with your renal team

Before starting any new vitamin or supplement, share the full label with your GP, renal pharmacist, dietitian or nephrologist. They will already know your blood results, prescribed phosphate binders, vitamin D regime and any active medication interactions — and can confirm whether a evidence-based daily supplement is appropriate alongside your current plan.

If you are on dialysis, are pregnant, are breastfeeding, or have had a kidney transplant, this conversation matters even more. The guidance on this page is general education, not a substitute for personalised clinical advice.

Vitamins for CKD Stage 3
Related reading: Vitamins for CKD Stage 3.

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • Cook from scratch when you can
  • Read sodium labels (≤ 0.3 g per 100 g is low)
  • Take any concerns to your GP or renal team early

Clinical guidance

TL;DR summary

eGFR estimates kidney filtering capacity from a blood creatinine test. Normal is ≥90. Stages 3a–3b (30–59) are moderate CKD; under 15 is kidney failure. A single low result should be repeated. Creatine supplements and dehydration can artificially lower eGFR.

Key takeaways
  • eGFR is an estimate, not a direct measurement.
  • UK uses the CKD-EPI 2021 equation (no ethnicity adjustment).
  • Normal is generally ≥ 90 mL/min/1.73 m².
  • A single low eGFR should be repeated, ideally within 2 weeks.
  • Creatine, dehydration and some medicines can affect the result.
Kidney Diet & Nutrition Considerations

Diet is one of the most powerful tools you have to look after your kidneys. UK renal guidance points to a Mediterranean-style, reduced-salt pattern: plenty of vegetables, lower-potassium fruit, whole grains, sensible protein, beans and pulses in moderation, oily fish and olive oil. Personal targets — for potassium, phosphate, protein and fluid — should be set by your renal team based on your bloods.

Foods to prioritise

  • Vegetables, lower-potassium fruit and whole grains
  • Sensible portions of fish, eggs, chicken or tofu
  • Olive oil and unsalted nuts in small amounts

Foods to limit

  • Added salt and ultra-processed foods
  • Phosphate additives in processed meats and ready meals
  • Sugary and energy drinks

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

What is eGFR?

eGFR stands for estimated Glomerular Filtration Rate. It is a calculated estimate of how much blood your kidneys filter per minute, based on a blood creatinine measurement plus age and sex. It is reported as mL/min/1.73 m².

What is a normal eGFR?

An eGFR of 90 or above with no other signs of kidney damage is generally considered normal. eGFR naturally falls slightly with age. The UK uses the CKD-EPI 2021 equation, which no longer adjusts for ethnicity.

What do the CKD stages mean?

Stage 1: eGFR ≥90 with kidney damage. Stage 2: 60–89 with damage. Stage 3a: 45–59. Stage 3b: 30–44. Stage 4: 15–29. Stage 5: under 15 (kidney failure). Stages 1–2 require evidence of kidney damage (e.g. protein in the urine).

Why does my eGFR change between tests?

eGFR can vary day-to-day due to hydration, recent high-protein meals, intense exercise, certain medicines (e.g. trimethoprim, cimetidine), and lab variation. UK guidance is to confirm a low result with a repeat test, ideally within 2 weeks.

Can supplements affect eGFR?

Creatine supplements can raise blood creatinine and lower the calculated eGFR without truly affecting kidney function. High-dose vitamin C and some herbal products can also interfere. Tell your GP about all supplements before kidney blood tests.

What should I do if my eGFR is low?

Discuss with your GP. They will usually repeat the test, check urine for protein (ACR), measure blood pressure, and review medicines. Most people with mildly reduced eGFR remain stable with good blood pressure and diabetes control.

What foods are good for kidney health?

A Mediterranean-style, mostly plant-based, reduced-salt diet is the most consistent evidence-based pattern for kidney health. Build meals around vegetables, lower-potassium fruit, whole grains, fish, eggs or tofu, beans and pulses in moderation, and olive oil.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Written by a UK Consultant Nephrologist

Professor Mohammed Mahdi Althaf (GMC 7216325) leads our clinical content.

Plain-English explanations

No jargon — designed to help patients understand their own results.

Supplement-aware

We explain how common supplements can affect kidney blood tests.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). Nephrologist Developed Daily Multivitamin.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • No Added Iron
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

View Full Biography

Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

View professional profile →
View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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