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Kidney

Urea (BUN): low protein intake, malnutrition and the value

According to the Cleveland Clinic, the liver makes urea, the waste product left when the body breaks down protein from food, and the kidneys filter it out of the blood.

According to MedlinePlus, a lack of protein in the diet and malnutrition can bring urea below normal, while according to MedlinePlus a high value may be a sign of kidneys that are not working well. Only a blood test shows where the urea stands.

Certe uses 2.5 to 7.5 mmol/l for urea in men and women above 18.

Doctor's Assessment Included

Urea is a waste product formed when protein is broken down, which the kidneys filter out of the blood. According to MedlinePlus, a high urea may point to kidneys not working well, but dehydration and eating a lot of protein can also raise the value.

  • Certe uses 2.5 to 7.5 mmol/l for urea above 18, Diagnostiek voor U 2.5 to 6.4 mmol/l and Unilabs 2.5 to 6.4 mmol/l from 18 to 60.
  • Star-SHL uses bands for urea by age and sex, such as 2.9 to 8.6 mmol/l in men and 2.5 to 7.0 mmol/l in women, both aged 19 to 50 inclusive.
  • According to the Cleveland Clinic, a low urea is not common and can be due to, among other things, too little protein or liver disease.

Reference Ranges

See the value that applies to you:

Choose male or female — this range differs by sex.

Enter your age — this range changes with age.

This range also depends on context such as cycle phase or sample material; the highlighted rows apply to your group.

Your reference range
mmol/l
2,2 14,2 mmol/l
Reference ranges by group, in mmol/l
Male · 6–12 years 2,8–7,1 mmol/l
2,8 7,1
Male · 13–18 years 2,7–7,6 mmol/l
2,7 7,6
Male · 19–50 years 2,9–8,6 mmol/l
2,9 8,6
Male · 51–65 years 3,2–9,8 mmol/l
3,2 9,8
Male · 66–80 years 3,6–11,8 mmol/l
3,6 11,8
Male · 81 years and older 4,3–14,2 mmol/l
4,3 14,2
Female · 6–12 years 2,4–7,3 mmol/l
2,4 7,3
Female · 13–18 years 2,2–6,9 mmol/l
2,2 6,9
Female · 19–50 years 2,5–7 mmol/l
2,5 7
Female · 51–65 years 2,9–9,4 mmol/l
2,9 9,4
Female · 66–80 years 3,1–11,8 mmol/l
3,1 11,8
Female · 81 years and older 3,6–13,9 mmol/l
3,6 13,9
2,2 14,2 mmol/l

Source: NVKC Reference population: Dutch general-practice population (NUMBER, n = 7,574,327)

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

Urea (BUN): what Dutch laboratories use

Reference ranges by group, in mmol/l
Star-shl · Male · 19–50 years 2.9–8.6 mmol/l
2.9 8.6
Star-shl · Female · 19–50 years 2.5–7.0 mmol/l
2.5 7
Star-shl · Male · 51–65 years 3.2–9.8 mmol/l
3.2 9.8
Star-shl · Female · 51–65 years 2.9–9.4 mmol/l
2.9 9.4
Star-shl · Male · 66–80 years 3.6–11.8 mmol/l
3.6 11.8
Star-shl · Female · 66–80 years 3.1–11.8 mmol/l
3.1 11.8
Star-shl · Male · 81 years and older 4.3–14.2 mmol/l
4.3 14.2
Star-shl · Female · 81 years and older 3.6–13.9 mmol/l
3.6 13.9
Unilabs · Everyone · 18–60 years 2.5–6.4 mmol/l
2.5 6.4
Unilabs · Everyone · 60 years and older 2.9–7.5 mmol/l
2.9 7.5
Certe · Everyone · 18 years and older 2.5–7.5 mmol/L
2.5 7.5
Diagnostiek voor U · Everyone 2.5–6.4 mmol/L
2.5 6.4
0 15.62 mmol/l

Source: Star-shl

Source: Unilabs

Source: Certe

Source: Diagnostiek voor U

Each value as the laboratory itself publishes it, retrieved in 2026.

Urea (BUN): what this test measures

A urea test expresses the amount of urea in the blood in millimoles per litre (mmol/l); Certe bases its adult limits on a 2005 consensus of the Vereniging Klinische Chemie Noord-Nederland.

Urea (BUN): why this value matters

A diet low in protein can show up in urea: according to MedlinePlus, both a lack of protein and malnutrition can give a lower-than-normal urea.

Urea (BUN): how the blood test works

Referral
No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
The draw
A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

Urea (BUN): when is testing worthwhile?

According to MedlinePlus, a urea test often belongs to a series of tests called a comprehensive metabolic panel and may be done at a routine checkup; if another test needs fasting blood, according to the Cleveland Clinic that means eight to 12 hours without eating or drinking.

Urea (BUN): symptoms of a high or low value

Low Levels

According to MedlinePlus, a low urea may be due to a lack of protein in the diet or malnutrition, and according to the Cleveland Clinic also to liver disease or too much water in the body.

High Levels

According to the Cleveland Clinic, a urea above the limit may suggest kidneys working less well, or be due to eating a lot of protein, dehydration or bleeding in the gastrointestinal tract.

Urea (BUN): causes of a low or high value

What lowers the value

  • Not eating enough protein

    A lack of protein in the diet can give a lower-than-normal urea.

  • Malnutrition

    Malnutrition is a possible reason for a lower-than-normal urea.

  • Too much water in the body (overhydration)

    Having too much water in the body is a possible cause of low urea.

  • Liver disease

    Liver disease is a possible cause of low urea.

What raises the value

  • Kidneys not working well

    Higher-than-normal urea levels may be a sign that the kidneys are not working well.

  • Dehydration

    Even with kidneys working properly, urea can rise from dehydration.

  • Eating a lot of protein

    Eating a lot of protein is a possible cause of high urea with kidneys working properly.

  • Bleeding in the gastrointestinal tract

    Gastrointestinal bleeding is on the list of possible causes of high urea.

  • Certain medicines

    Certain medicines, including carbamazepine, methotrexate and tetracycline, can raise urea.

Urea (BUN): lifestyle and this value

According to the Cleveland Clinic, most people should consume 40 to 60 grams of protein a day, and with a high urea less protein may be needed. Discuss an abnormal urea with your GP before you change your protein intake.

Urea (BUN): frequently asked questions

Can eating little protein lower urea?

Yes, according to MedlinePlus and the Cleveland Clinic, a lack of protein in the diet can bring urea below normal.

Urea (BUN): sources

  1. den Elzen WPJ, Brouwer N, Thelen MH, Le Cessie S, Haagen I-A, Cobbaert CM. NUMBER: standardized reference intervals in the Netherlands using a 'big data' approach. Clin Chem Lab Med 2018;57(1):42-56. (retrieved 2026) doi.org
  2. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  3. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
  4. Certe, Bepalingenwijzer (referentiewaarden per bepaling), bepalingenwijzer.certe.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenwijzer.certe.nl
  5. Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
  6. MedlinePlus, BUN (Blood Urea Nitrogen), medlineplus.gov, geraadpleegd 2026-10-18 (retrieved 2026) medlineplus.gov
  7. Cleveland Clinic Health Library, Blood Urea Nitrogen (BUN) Test, my.clevelandclinic.org, geraadpleegd 2026-10-18 (retrieved 2026) my.clevelandclinic.org

Tests with related values

These panels measure values from the same category as this marker.

GLP-1

GLP-1 Check-in Panel

The 3-month safety and progress check clinics do: pancreas, liver, kidneys, salts and your metabolic progress on GLP-1 medication.

ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) Potassium Sodium Glucose (Fasting) Total Cholesterol Lipase Creatinine Triglycerides eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€109,-
GLP-1

GLP-1 Baseline Panel

Your starting point before the first injection: blood sugar, cholesterol, pancreas, liver, kidneys, thyroid and nutrients in one measurement.

Insulin (Fasting) ALT (Alanine Aminotransferase) TSH (Thyroid Stimulating Hormone) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) Bilirubin (Total) ApoB (Apolipoprotein B) Vitamin B12 Ferritin Potassium Sodium Glucose (Fasting) Total Cholesterol Albumin Lipase Creatinine Vitamin D (25-OH) Triglycerides Bilirubin (Direct) Bilirubin (Indirect) HOMA-IR eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€214,-
GLP-1

GLP-1 Extended Panel

The 6-month measurement: everything from the check-in plus insulin, ApoB and your nutrients — especially relevant if you have been eating much less for a while.

Insulin (Fasting) ALT (Alanine Aminotransferase) AST (Aspartate Aminotransferase) HDL Cholesterol HbA1c (Glycated Hemoglobin) ApoB (Apolipoprotein B) Vitamin B12 Ferritin Potassium Sodium Glucose (Fasting) Total Cholesterol Albumin Lipase Creatinine Vitamin D (25-OH) Triglycerides HOMA-IR eGFR (Estimated Glomerular Filtration Rate) LDL Cholesterol Cholesterol/HDL Ratio Non-HDL Cholesterol LDL/HDL Ratio
€196,-

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Medical policy
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Urea (BUN)

€7,-