Urine Amorphous Sediment

Tiny shapeless grains seen in urine under the microscope. They are often harmless and commonly form as a sample cools.

AI-drafted. Awaiting verificationLOINC 105111-9

What it is

Amorphous means without shape. Amorphous sediment is a haze of very small grains, usually urate or phosphate crystals, that a lab sees when it looks at urine under a microscope. Some labs print amorphous sediment when they don't say which of the two it is. It is usually reported in words such as none, few, moderate or many.

Why it matters

Crystals can show up in the urine of healthy people, and they often form after the sample is collected, once it cools or sits. That means amorphous sediment usually says more about the sample than about your body. Clinicians read it alongside the urine pH, color, cloudiness and the rest of the urinalysis.

If it’s high

Many amorphous grains most often reflect a sample that cooled or stood before it was tested, or urine that was very concentrated. On its own it rarely points to a specific condition. Your clinician reads it together with your symptoms and the other urinalysis results.

Common causes

A sample that cooled or was refrigerated before testing, which makes crystals form
A normal finding in a healthy person
Low urine volume, meaning concentrated urine
Alkaline urine, which favors amorphous phosphates
Acidic urine, which favors amorphous urates

What can help

Take the sample to the lab promptly, and keep it as the lab instructs
Ask whether the lab can say if the grains are urates or phosphates, and whether the urine pH was checked
Ask whether a repeat on a fresh sample would help if your clinician is concerned

What can affect your result

Sample temperature and time: cooling, refrigeration and standing change which crystals form or dissolve
Urine pH: alkaline urine favors amorphous phosphates, and acidic urine favors urates
How concentrated the urine is
Diet and how much you drink
How your lab reports it: in words, or per microscope field
Urine that cools or is refrigerated before testing can form crystals, including amorphous grains, that were not in the bladder.
Urine that stands for a long time can also lose crystals, so a delayed sample can read lower.
Alkaline urine tends to form amorphous phosphates, and labs sometimes add a little dilute acid to dissolve them so other particles are easier to see.

Any time. A midstream sample taken to the lab promptly gives the most reliable crystal findings, because fresh, warm urine has not had time to form new crystals. Not applicable. The finding reflects the sample, including how it was stored, more than a lasting change in your body.

When to talk to a clinician

Amorphous sediment alone is not a reason for urgent care. If you have severe pain in your side or back, blood in your urine, burning when you urinate or a fever, contact a clinician whatever this result says.

Questions you could ask

Is there anything in this urinalysis that I should recheck?
Was my sample fresh when it was tested?
Does my urine pH or the rest of my urinalysis change how you read this?
Would a repeat sample be useful?

Questions people ask

Does amorphous sediment mean I have kidney stones?

No. Amorphous grains by themselves don't show kidney stones, and crystals can appear in healthy urine. If you have pain in your side or back, or blood in your urine, tell your clinician.

Why does my report say amorphous sediment instead of urates or phosphates?

Both look like fine grains under the microscope, and some labs don't separate them. The urine pH can hint at which one it is. Some reports list urates and phosphates separately.

Can a sample that sat too long cause this?

Yes. Crystals often form when urine cools or is refrigerated. That is one reason labs prefer a fresh sample.

Show the science and sources

For clinicians and researchers

Amorphous sediment is a granular, non-crystalline precipitate in the urine sediment. Amorphous urates form in acidic urine and amorphous phosphates (calcium and magnesium phosphate) in alkaline urine; a 2024 nephrology review tabulates urine pH 5.8 or lower for amorphous urates and 7.0 or higher for amorphous phosphates, and StatPearls links amorphous phosphates to alkaline urine, low urine volume and a calcium-rich diet. Both sources list normal subjects among the associations, and the nephrology review also lists refrigerated samples, so the finding often reflects the sample rather than disease. A 2022 Laboratory Medicine study found that amorphous urates formed in concentrated, acidic urine and that prewarming the specimen to 60 C for 90 seconds dissolved most of them. Both types appear as fine granules under routine microscopy, so some labs report them together as amorphous sediment, and urine pH helps tell them apart. Dilute acetic acid dissolves phosphates in alkaline urine (Clinical Methods, Urinalysis chapter), and refrigeration can precipitate uric acid crystals that rewarming redissolves. Labcorp notes that crystalluria is frequently seen in urine stored at room temperature or refrigerated, and that crystals are diagnostically useful mainly when seen in warm, fresh urine. Crystalluria is uncommon in warm, fresh urine because of crystal inhibitors and the short time before collection. In LOINC, amorphous sediment has presence, count-per-area and automated variants; the codes listed here are the presence codes, and amorphous urates and phosphates also have their own codes.

LOINC 105111-9 (primary), 105888-2, 8246-1. Specimen: urine.

Sources

Urinalysis, StatPearls Publishing (NCBI Bookshelf) (2023)
Urinalysis: A Comprehensive Review, American Family Physician (2005)
Clinical Methods: Chapter 191, Urinalysis, Butterworths (NCBI Bookshelf) (1990)
Urinalysis, Complete With Microscopic Examination (test 003772), Labcorp
Diagnostic Utility of Urine Microscopy in Kidney Diseases, Indian Journal of Nephrology (2024)
Protocols to Dissolve Amorphous Urate Crystals in Urine, Laboratory Medicine (2022)

AI-drafted. Awaiting verification. Last reviewed 2026-10-03. How we build and check these pages.