Crystals in Urine: Are They Normal or a Sign of Kidney Stones?

Crystals in urine are tiny solid particles that form when minerals or other substances become too concentrated in urine. MedlinePlus states that having a few small crystals in urine is normal and usually causes no problems. Large amounts of certain types, however, can be linked to kidney stones or other conditions that need treatment.

The finding is called crystalluria. It is usually reported from the microscope part of a urinalysis, which also looks at cells, casts and bacteria. Cleveland Clinic notes that crystals can be found in people who are completely healthy, so the result needs to be read alongside your symptoms and the rest of the test.

A crystal finding on its own rarely needs urgent care. Symptoms around it matter more. The NHS advises an urgent GP appointment or NHS 111, or the equivalent urgent service where you live, if you think you have kidney stones and you have severe pain or a high temperature, or feel hot, cold or shivery.

• Severe pain in the side, back, lower abdomen or groin, which may come and go
• Fever, chills or shivering with urinary symptoms
• Blood in the urine, or pink, red or brown urine
• Nausea or vomiting with pain

The lab identifies crystals mainly by their shape under the microscope. The acidity of your urine (its pH) affects which types form. MedlinePlus and Cleveland Clinic describe several types.

• Calcium oxalate: one of the most common types. Calcium oxalate and calcium phosphate are the most common cause of kidney stones.
• Uric acid and urates: tend to form in acidic urine. Large amounts may occur with conditions such as gout or type 2 diabetes.
• Struvite, also called triple phosphate: often linked to alkaline urine and repeated urinary tract infections.
• Amorphous crystals: material with no clear shape, often reported as amorphous urates or amorphous phosphates.
• Cystine and xanthine: uncommon. Cleveland Clinic notes they indicate rare inherited disorders, such as cystinuria.

Amorphous simply means the crystals have no definite shape. They are usually reported as urates or phosphates. Because crystals can appear in the urine of healthy people, a few amorphous crystals in an otherwise normal sample, with no symptoms, are often of little concern on their own.

One reason is timing. American Family Physician notes that crystals can form in normal urine as it cools, which is why only fresh samples should be analysed for crystals. Cloudy urine is also often caused by phosphate crystals settling out of alkaline urine. If a sample stood for a while before testing, the crystals may not reflect what is happening in your body.

How the sample is collected also matters. MedlinePlus describes a clean-catch method: clean the genital area, pass a little urine into the toilet first, then collect the midstream portion in the container. Tell the person taking the sample if you are menstruating or have bleeding haemorrhoids, as this can affect the result. Following the instructions carefully gives the most reliable reading.

Ask your clinician whether the amorphous finding needs any follow-up, or whether it can be set aside in your case.

Cleveland Clinic explains that crystals form when there are too many minerals in urine and not enough liquid. Common contributors include:

• Not drinking enough fluids, which concentrates the urine
• A diet high in animal protein or salt
• Urine that is too acidic or too alkaline
• Urinary tract infections, especially for struvite crystals
• Certain medicines, including some antibiotics, antivirals, diuretics and calcium-based antacids
• Rarer causes, such as inherited metabolic conditions or poisoning with ethylene glycol

Not necessarily. Crystals and stones are related but not the same. MedlinePlus explains that some types of crystals can stick together and grow into stones. People who form stones often have crystals in their urine, but many people with crystals never develop a stone.

Small stones may pass with little or no pain. Larger stones can block the flow of urine and cause pain, bleeding and, if the blockage persists, kidney damage. This is why crystals reported alongside pain, blood in the urine or signs of infection are taken more seriously than crystals found on a routine check with no symptoms.

A crystal test can help find the likely stone type in someone who has had stones, which guides prevention. For a fuller picture, a clinician may arrange a 24-hour urine collection, which MedlinePlus notes may be more accurate because crystal levels vary through the day. If a stone has already been seen on a scan, size and symptoms guide what happens next.

Fluids are the main way to keep urine dilute. NIDDK describes drinking enough liquid, mainly water, as the most important thing you can do to prevent kidney stones. The NHS suggests checking your urine colour, since dark urine suggests you need more fluids.

How much you should drink depends on your health. People with kidney failure or a fluid restriction should follow their own team's advice. NIDDK also advises not cutting out calcium without advice, and the NHS recommends speaking to a doctor before making big diet changes.

Take the full urinalysis report with you. These questions can help clarify what the result means for you.

• Which type of crystals were seen, and how many?
• Was the sample fresh, and could the result reflect cooling or storage?
• Do the other parts of my urine test, such as blood or infection markers, change how you read this?
• Do I need a repeat sample, a 24-hour urine test or a scan?
• Could any of my medicines be contributing?
• How much should I drink, given my other health conditions?

On SameCase, patients and verified doctors share de-identified cases. Seeing how others with similar urine results were followed up, which tests they had and what questions they asked can help you prepare for your own appointment. Other cases cannot explain your result, and decisions about tests and treatment belong with your care team.