What is Amino Acids Urine test? 

Amino acids urine test determines the level of amino acids present in your urine.

Amino acids are the building blocks of proteins which perform several important functions in our body. Our body needs 20 different amino acids for its growth and development. These are broadly classified as essential and non-essential amino acids. Essential amino acids are obtained from dietary sources, whereas non-essential amino acids are produced in the body. 

Amino acids are also needed for energy production, synthesis of hormones, neurotransmitters (chemical messengers that carry signals from one nerve cell to the other) and melanin (skin pigment) in the body. 

Excess amino acids are converted to urea in liver and expelled through kidneys with urine.  Dysfunction in either of these organs or a metabolic error may increase the urine amino acid levels. An amino acid urine test is mainly done to check for abnormalities related to either the metabolism or transport of an amino acid that usually manifest in the form of high urine amino acids.

  1. Why is Amino Acids Urine test performed?
  2. How do you prepare for an Amino Acids Urine test?
  3. How is an Amino Acids Urine test performed?
  4. What do Amino Acids Urine test results mean?

Doctors order an amino acids urine test if they suspect inborn errors of metabolism - usually observed during infancy and early childhood. 

The signs and symptoms of these metabolic errors include:

  • Inability to thrive
  • Problems with digestion
  • Growth retardation
  • Neurological symptoms such as seizures
  • Liver dysfunction
  • A sweet smell (like that of maple syrup) in urine

If left untreated during childhood, it may lead to mental retardation, poor growth, developmental delays and death.

This test is also used to evaluate acquired conditions such as liver disease, renal failure, burns, nutritional disturbances, neurological disorders and muscle diseases.

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No special preparation is required for this test. If you are taking any prescribed, non-prescribed or illegal medications, please inform your doctor. He/she may advise you to discontinue medications such as amphetamines, norepinephrine, levodopa and certain antibiotics before the test, as they may affect the test results. Factors such as the patient’s age, diet, sleeping pattern and pregnancy may also affect the test results. So, make sure you give your complete medical history to your doctor.

The test is performed on a 24-hour urine sample. Your healthcare practitioner will explain the procedure to you before it is performed. You will be provided with a special container to collect the sample. Here is the right way to collect a 24-hour urine sample:

  • Wash and clean your hands properly using disinfectant before collecting the sample 
  • At the start of the 24-hour collection period, empty your bladder completely and discard this first urine specimen. Note the time. 
  • Collect all the urine voided over the next 24 hours in the container provided 
  • Make sure you refrigerate the container during the entire 24 hours
  • Label the sample and deliver it to the laboratory for testing

If the urine test is ordered for your baby, take a collecting bag (a plastic bag with adhesive tape) from the laboratory and follow these steps: 

  • Clean the genital area of your baby with cleaning wipes.
  • For a baby boy, place the entire penis in the collecting bag and stick the adhesive tape to the skin. For a baby girl, stick the bag over the labia.
  • Now, place a diaper over the bag to secure it. 
  • Collect the urine for the next 24 hours by emptying the collecting bag into a container
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Normal results:

Some amount of each amino acid may normally be present in the urine. 

The reference ranges for different amino acids in the urine are listed in the table below. These values may vary slightly from one laboratory to another. Please discuss your test results with your doctor to know precisely what they signify for you. 

Amino acids Concentration in urine in micromoles/decilitre (µmol/dL)
Children Adults
Alanine 65-190 160-690
Arginine 10-25 13-64
Asparagine 15-40 34-100
Aspartic acid 10-26 14-89
Cystine 11-53 28-115
Glutamic acid 13-22 27-105
Glutamine 150-400  300-1040
Glycine 195-855 750-2400
Histidine 46-725 500-1500
Isoleucine 3-15 4-23
Leucine 9-23 20-77
Lysine 19-140 32-290
Methionine 7-20 5-30
Phenylalanine 20-61 36-90
Proline Not measured Not measured
Serine 93-210 200-695
Threonine 25-100 80-320
Tyrosine 30-83 38-145
Valine 17-37 19-74

Table: Reference ranges for some important amino acids in the urine

Abnormal results:

Elevated levels of amino acids in the urine may be seen in the following conditions:

  • Alkaptonuria (a metabolic disorder causing black urine and painful, swollen joints)
  • Canavan disease
  • Fructose intolerance
  • Galactosaemia (a disorder caused by an inability to metabolise galactose sugar)
  • Hartnup disease (a disorder caused by defective transport of certain amino acids) 
  • Hyperparathyroidism
  • Maple syrup urine disease
  • Multiple myeloma (a type of cancer)
  • Ornithine transcarbamylase deficiency
  • Osteomalacia and rickets (disorders of weak and deformed bones)
  • Tyrosinaemia types I and II (a genetic disorder characterised by high levels of the amino acid tyrosine in the body)
  • Viral hepatitis (liver disease due to viral infection)
  • Wilson's disease (liver degeneration due to abnormal copper metabolism)
  • Liver disease or necrosis (tissue death)
  • Renal disease and renal failure
  • Cystinosis
  • Progressive muscular dystrophy

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.


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  2. South Tees Hospitals. NHS Foundation trust. National Health Service, U.K. Amino Acids (CSF, Plasma & Urine)
  3. Cleveland Clinic. [Internet]. Cleveland. Ohio. Technical Update: December 2018
  4. Fischbach FT. A Manual of Laboratory and Diagnostic Tests. 7th ed. 2003. Lippincott Williams & Wilkins Publishers. Pp: 38, 119, 174, 176, 198, 730.
  5. Benioff Children's Hospital [internet]: University of California, San Francisco; Plasma Amino Acids
  6. Chau K, Hutton H, Levin A. Laboratory assessment of kidney disease: glomerular filtration rate, urinalysis, and proteinuria. In: Skorecki K, Chertow GM, Marsden PA, Taal MW, Yu ASL, eds. Brenner and Rector's The Kidney. 10th ed. Philadelphia, PA: Elsevier; 2016:chap 26.
  7. Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 114.
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