Skip to content
Blood Test Tracker

Urine Uric Acid Crystals

Whether uric acid crystals show up in a urine sample. They are common in acidic or concentrated urine and are often harmless.

AI-verified against cited sources. Awaiting expert reviewLOINC 5817-2

What it is

Uric acid crystals form when there is a lot of uric acid in urine that is acidic. Under the microscope they are yellow to orange-brown and often look like diamonds or barrels. Labs report them as present or absent, as a number per high-power field (HPF), or in words such as few or many.

Why it matters

Crystals can turn up in healthy people, especially when urine is concentrated or has cooled, so a few are usually not a concern. Their main value is as a clue. Together with acidic urine, a low urine volume, or a high uric acid level in blood or urine, they can fit with a tendency to form uric acid kidney stones. Your clinician reads this finding with your symptoms and other tests, and crystals alone do not mean you have a stone.

If it’s high

More uric acid crystals than usual mostly reflect acidic, concentrated urine. Common reasons are not drinking much, a diet high in protein, or a sample that cooled before it was tested. Less often they go along with high uric acid levels, gout or kidney stones.

Common causes

  • Acidic urine (low pH), which varies with diet
  • Concentrated urine from not drinking enough fluid
  • A sample that cooled or stood before it was tested
  • More uric acid than usual in the urine, from diet, gout or other causes
  • Uric acid kidney stones, which are less common

What can help

  • Give a fresh clean-catch sample and get it to the lab promptly
  • Ask whether a urine pH check or a 24-hour urine uric acid test would add useful information
  • Ask how much fluid is right for you if you have had kidney stones

What can affect your result

  • Urine pH: acidic urine favors these crystals
  • How concentrated the urine is
  • Diet and fluids, including high-protein foods
  • How fresh and how cool the sample is
  • How your lab reports crystals
  • Crystals can form in normal urine as it cools, so a sample that sat or was refrigerated before testing can show crystals that were not there when you gave it (AFP 2022).
  • Concentrated urine, for example after little fluid or heavy sweating, makes crystals more likely.
  • Diet affects urine pH: a high-protein diet and acidic fruits can lower it, which favors uric acid crystals (AFP 2022).
  • Labs report crystals differently: present or absent, per high-power or low-power field, or in words. Some labs list amorphous urates as a separate finding.

A fresh midstream clean-catch sample. Crystals can form as urine cools, so labs prefer fresh samples. Reflects the sample on the day. Crystals can appear or disappear as urine pH and concentration change through the day.

When to talk to a clinician

Seek care promptly for severe pain in your side or back, especially with nausea, fever, blood in your urine or trouble passing urine, whatever this finding says. A sudden, hot, swollen, painful joint is another reason to be seen soon.

Questions you could ask

  • Does this matter given any stone or gout history I have?
  • Do my urine pH and blood uric acid level fit with this finding?
  • Would a 24-hour urine test be useful?

Questions people ask

Do uric acid crystals in my urine mean I have gout?

No. Gout comes from urate crystals in the joints and is tied mainly to the uric acid level in the blood. Crystals in a urine sample are a separate finding and often just reflect acidic, concentrated urine.

Should I change my diet because of this?

Ask your clinician before making changes because of this finding alone. They can tell you whether it fits with your urine pH, blood uric acid and history, and whether anything would help.

Show the science and sources

For clinicians and researchers

AFP 2005 describes uric acid crystals as yellow to orange-brown and diamond- or barrel-shaped, and notes that crystals may be seen in healthy people. AFP 2022 adds that uric acid crystals are birefringent under polarized light, that crystals can form in normal urine when it cools so only fresh samples should be examined, that urine pH ranges from 4.5 to 8 and is usually 5.5 to 6.5, and that a low pH occurs with uric acid, cystine and calcium oxalate stones and with diets high in protein and acidic fruits. Ng 2021 lists three main factors for uric acid stones: urinary pH below 5.5, low urinary volume and hyperuricosuria, alone or together. The Brazilian nephrolithiasis guideline treats a 24-hour urine pH below 5.5 as a pointer to uric acid stone disease and states that uricosuria matters mainly when read together with urinary pH; MedlinePlus lists 250–750 mg/24 h as the usual range for 24-hour urine uric acid. This entry maps to generic urate crystals; LOINC also has separate codes for sodium urate, ammonium urate and amorphous urates, which labs may report as their own findings. There is no standard reference interval or grading, so grades are stored as an ordered scale.

LOINC 5817-2 (primary), 46138-4, 40485-5, 99903-7. Specimen: urine.

Sources

  1. Urinalysis: A Comprehensive Review, American Family Physician (2005)
  2. Office-Based Urinalysis: A Comprehensive Review, American Family Physician (2022)
  3. Medical evaluation and pharmacotherapeutical strategies in management of urolithiasis, Therapeutic Advances in Urology (2021)
  4. Brazilian Guidelines on evaluation and clinical management of Nephrolithiasis: Brazilian Society of Nephrology, Jornal Brasileiro de Nefrologia (2025)
  5. Uric acid urine test, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Related markers