Foamy Urine 2 Months After a Kidney Transplant but Tests Are Normal: Ordinary Bubbles vs Protein Leak, Do Anti-Rejection Drugs Play a Role, What UPCR Means, and Warning Signs for the New Kidney

Reader question: two months after a kidney transplant, the urine still looks foamy, the doctor says tests are normal, but I am still worried

A member of a kidney transplant support group shared that her partner had a kidney transplant a little over two months ago and his urine still looks foamy. The doctor said the test results were normal, but she still worries that something is wrong with the new kidney.

Short answer: foam alone does not mean protein is leaking. The blood and urine results the doctor reviews are far more accurate than looking at the toilet. What family can do is ask which values “normal results”
included, help with on-time medicines, and keep a list of warning signs that need an immediate call to the transplant center.
If urinary infection is a worry, read
Frequent infections after a kidney transplant: anti-rejection drugs, bathroom hygiene and UTI prevention

1. What causes foam in urine, and how much can the eye tell?

Direct answer: foam forms when the urine stream hits the toilet water and drags air in. Ordinary bubbles usually pop quickly, while albumin is a protein that coats the bubble surface and keeps foam stable for longer.
But looking at foam cannot reliably tell ordinary bubbles from protein leak; a urine test is needed.

Causes of foam that are not protein leak

A review in the journal of the American Society of Nephrology notes that foamy urine is common in the general population and can come from forceful, rapid urination, concentrated urine, or cleaning products in the toilet.
Whether protein is leaking can only be told by a urine protein-to-creatinine or albumin-to-creatinine ratio
(Khitan 2019).

• Forceful stream: when the bladder is very full, its contraction makes the stream hit the water hard and pull in more air
• Concentrated urine: first-morning urine or urine on low-fluid days carries more dissolved substances, so foam forms more easily
• Height and force into the bowl: urinating standing up makes more foam than sitting
• Toilet cleaners: surfactants left in the bowl can foam on their own even with normal urine

Why protein makes foam last

Albumin has water-loving and water-repelling parts, so it lines up at the bubble surface and lowers surface tension, making the bubble wall stronger and slower to pop. Foam from heavy protein leak, as in nephrotic syndrome, is therefore often fine and long-lasting.
Smaller amounts of protein do not always make foam look clearly different.

How accurate is judging by eye?

A Korean study of 72 outpatients who came in because of foamy urine found clear protein leak in only 16 (22.2%). Among 38 who had albumin measured, 12 (31.6%) had albumin or protein leak
(Kang 2012).
So most people who notice foam have no protein leak, and some have protein leak they cannot see. This study was in general patients, not transplant recipients, but the principle holds.

2. Why there is still foam at 2 months while tests are normal

Direct answer: protein in the urine during the first weeks after transplant can come from the native kidneys still in the body and from new-kidney tissue that is recovering. This protein usually falls within a few weeks.
If tests are normal at 2 months, the foam you see is likely physical, but follow-up tests are still needed as scheduled.

Native-kidney protein falls quickly

Most patients keep their native kidneys, which may keep making some protein-containing urine for a while. In 14 living-donor recipients with a pre-transplant UPCR above 0.5, UPCR fell below 0.2
in everyone, at an average of 4.5 weeks (range 1–10 weeks)
(D’Cunha 2005).
The authors concluded that after this early period, any protein leak should be investigated in the new kidney.

Another study of 115 patients found urine protein fell from 3,650 mg a day before transplant to 550 mg a day at 3 weeks and 472 mg a day at 1 year
(Myslak 2006).

Averages from 115 patients (Myslak 2006); bar lengths are approximately proportional

Mild protein leak after transplant is common

A review found that 11–45% of kidney transplant recipients have urine protein at 1 year. It can come from small tubules injured during surgery that reabsorb small proteins poorly, or from damaged filter units
(Ponticelli 2012).
In 613 recipients, protein above 150 mg a day was found in 45% at 1 year, mostly below 500 mg a day
(Amer 2007).

Why doctors still track low-level protein

In 722 recipients, having urine protein at 1 year raised the risk of graft failure 2.03-fold and the risk of death 1.98-fold
(Roodnat 2001).
Protein above 1,500 mg a day mostly reflects filter-unit disease in the new kidney, so doctors check protein regularly and look for a cause when it rises
(Amer 2009).
Among 67 children with kidney transplants, 58% had protein above 500 mg a day at 3 months, and this group had more acute rejection
(Gulleroglu 2014).

3. What “normal results” include: UPCR, UACR, dipstick and creatinine

Direct answer: after a kidney transplant, doctors judge the new kidney’s function from blood creatinine and eGFR, and judge protein leak from the urine protein-to-creatinine ratio (UPCR)
or albumin-to-creatinine ratio (UACR). These values say far more than foam does.

Urine dipstick

A dipstick changes color when albumin is present and gives a quick screen, but the result depends on how concentrated the urine is. Concentrated urine may show a slight positive, and dilute urine may read negative despite protein.
Standard dipsticks also miss low-level albumin, so dipstick results usually need confirmation with UPCR or UACR.

Is a single-sample UPCR accurate enough?

A study of 133 kidney transplant patients compared 520 paired morning samples with 24-hour collections and found a correlation of 0.93, sensitivity of 97–99% and specificity of 95–99%
(Steinhäuslin 1995).
A single-sample UPCR can therefore replace a full-day collection for routine follow-up.

Normal values, and values that need review

Urine protein below 150 mg a day, or a UPCR below about 150 mg per gram of creatinine, is normal. Albumin below 30 mg a day is normal, not microalbuminuria.
Values of 30–300 mg a day are called moderately increased albumin. After week 3 of a transplant, protein of 1,500 mg a day or more, or a rise of more than 500 mg a day from baseline, is linked to filter-unit disease in the new kidney
(Myslak 2006).

How often to test under the KDIGO guideline

The KDIGO guideline for kidney transplant recipients advises weekly creatinine checks in months 2–3, and urine protein at least once in the first month, every 3 months during the first year, and yearly after that
(Kasiske 2010).
Each center may schedule tests more often based on the patient’s risk.

Table: tests used to check protein leak and new-kidney function

Normal values are general references; labs may use different units. Read them with the treating doctor.

• What was the latest creatinine, and how far is it from the post-transplant low point?
• How was urine protein tested: dipstick, UPCR or UACR, and what was the value?
• Is the tacrolimus level within target?
• Has BK virus been tested, and when is the next test?
• If foam is still seen every day, when should a repeat UPCR be collected?

4. Do anti-rejection drugs cause foam or protein leak?

Direct answer: calcineurin inhibitors constrict the incoming arteriole of each filter unit, which lowers filtering pressure; they are not a common cause of protein leak.
mTOR inhibitors are more strongly linked to protein leak. What matters with tacrolimus is a drug level that is too high or too low.

What tacrolimus and cyclosporine do to kidney blood vessels

A review of calcineurin inhibitor toxicity explains that these drugs constrict the incoming arteriole of the filter unit, so blood flow through the kidney and the filtration rate fall. This effect reverses when the drug level is adjusted.
Long-term use can damage small arteries, tubules and kidney tissue. Factors that increase toxicity include dehydration and salt depletion, and use of NSAID pain relievers
(Naesens 2009).

mTOR inhibitors are more strongly linked to protein leak

mTOR inhibitors such as sirolimus and everolimus are linked to more protein leak than calcineurin inhibitors
(Diekmann 2012).
In 613 recipients, 76% of those on sirolimus had protein leak compared with 40% of those not on it
(Amer 2007).
If the doctor switches to this class, follow-up UPCR tests will be scheduled.

What changes tacrolimus levels

Six organ recipients with infectious diarrhea all had tacrolimus levels rise to 20–60 ng/mL, returning to target after symptom treatment and dose adjustment
(Hochleitner 2001).
Foods and herbs that block the CYP3A4 enzyme, such as grapefruit, pomelo, pomegranate, ginger and turmeric, can raise tacrolimus levels, while St John’s wort lowers them
(Miedziaszczyk 2022).
For more on diarrhea and spicy food, read
Spicy food after a kidney transplant: anti-rejection drugs and diarrhea

Pain relievers to ask about first

NSAID pain relievers such as ibuprofen, naproxen and diclofenac raise the risk of kidney toxicity when used with calcineurin inhibitors
(Naesens 2009).
For pain or fever, ask the transplant team first what dose of paracetamol is allowed.

5. Home care: fluids, medicines and a daily log

Direct answer: what truly helps the new kidney is taking anti-rejection medicines on time, drinking the amount the center sets, not taking medicines or herbs that have not been cleared, and keeping a daily log so the transplant team sees changes early.

How much to drink

Use the fluid target your transplant center gave you, because it depends on body weight, new-kidney function, the heart and the weather. Drinking enough dilutes the urine, so foam from concentrated urine decreases.
But drinking more does not reduce protein that is truly leaking, and dehydration increases calcineurin inhibitor toxicity.

• Check urine color: pale yellow means enough fluid; dark urine in the daytime means drinking more as the center advises
• Hot days or heavy sweating: drink extra as advised; if there is heart disease or swelling, ask first
• Diarrhea, vomiting or fever: tell the center the same day, because fluid loss and drug levels change

How much does on-time dosing matter?

A systematic review found that about 22% of kidney transplant recipients take anti-rejection medicines irregularly, 36% of graft losses were linked to earlier irregular dosing,
and the odds of graft failure were 7 times higher in this group
(Butler 2004).
A Cochrane review found that reminder and education programs helped people take the full dose more often, but the evidence is of low quality
(Mellon 2022).

• Set two alarms: on the patient’s phone and a family member’s phone, at the same time every day
• Use a pill organizer by day and dose: refill it once a week together with family
• On drug-level test days: draw blood before the morning dose, then take the dose after the draw, as the center advises
• Missed dose: call the center to ask whether to take it now or skip it; do not double up on your own
• Every new medicine: including pharmacy medicines, herbs and vitamins, ask the transplant team first

A daily log that helps the transplant team

• If you want to log foam: note when it appears, whether it is first-morning urine, and how much was drunk that day; this helps the doctor separate foam from concentrated urine
• Photos are fine, no need to time it: use them when talking with the doctor, not to decide for yourself whether protein is leaking

6. Signs of rejection and infection to know

Direct answer: most rejection causes no symptoms and is found by a rising creatinine, so scheduled blood tests matter more than watching foam. Infection in a kidney transplant recipient may show only as fever or fatigue.

Rejection is often silent

A NEJM review of kidney rejection explains that with modern anti-rejection drugs, classic symptoms such as fever and pain over the new kidney are less common. Most rejection is found by rising creatinine or rising urine protein,
and confirmed by kidney biopsy
(Nankivell 2010).

Urinary tract infection in kidney transplant recipients

American Society of Transplantation guidance states that kidney recipients are at higher risk of urinary infection because of ureteral stents and surgery, and some have only fever, fatigue or a high white cell count.
The same guidance states that bacteria in the urine without symptoms after 2 months do not need antibiotics
(Goldman 2019).

BK virus: why scheduled blood tests matter even without symptoms

The 2024 international guideline advises testing blood for BK virus monthly until month 9, then every 3 months until 2 years, because this virus damages the new kidney without symptoms and tacrolimus is one risk factor
(Kotton 2024).

Table: comparing anti-rejection drugs and care steps related to urine protein

Drug class and generic names only. Each person’s regimen is set by the transplant team; do not change it yourself.

Common beliefs vs the evidence

Foamy urine means the new kidney is leaking protein

Not correct. Among people who saw a doctor for foamy urine, only 22.2% had clear protein leak. A urine test is what decides.

Tacrolimus makes protein slip out as temporary foam

No evidence supports this. The drug constricts the incoming arteriole and lowers filtering pressure. The class more linked to protein leak is mTOR inhibitors.

Foam that clears in 1–2 minutes means you are safe

No study has set this time. Foam that clears fast does not rule out protein leak; UPCR or UACR results are needed.

Drinking lots of water makes protein leak go away

Water dilutes urine and reduces foam, but does not reduce protein that is truly leaking, and drinking more than the center advises may not suit people with heart disease or swelling.

One normal result means no more testing

Not correct. The KDIGO guideline advises weekly creatinine in months 2–3 and urine protein every 3 months during the first year.

Kidney tonic herbs make the new kidney stronger

There is no evidence they help, and some change tacrolimus levels enough to cause kidney toxicity or raise rejection risk. Ask the transplant team first every time.

Frequently Asked Questions (FAQ)

Why is urine still foamy 2 months after a kidney transplant when the doctor says results are normal?

Most foam comes from a forceful stream hitting the toilet water or from concentrated urine in the morning and on low-fluid days. Normal results mean creatinine is stable and urine protein is within range, which is more accurate than looking at foam. If you are still worried, ask for a repeat UPCR at the next visit.

How can you tell ordinary bubbles from protein foam?

Ordinary bubbles are usually large, clear and pop quickly, while protein foam is often fine and lingers, but the eye cannot tell reliably. Among 72 people who saw a doctor for foamy urine, only 22.2% had clear protein leak. The deciding test is a urine UPCR or UACR.

What UPCR or UACR value is normal?

A UPCR below about 150 mg per gram of creatinine and a UACR below 30 mg per gram are normal. After week 3 of a transplant, protein of 1,500 mg a day or more, or a rise of more than 500 mg a day from baseline, is linked to filter-unit disease in the new kidney and needs review by the doctor.

Do anti-rejection drugs like tacrolimus cause foamy urine or protein leak?

Tacrolimus and cyclosporine constrict the incoming arteriole of the filter unit and lower filtering pressure, so they are not a common cause of early protein leak. The class more linked to protein leak is mTOR inhibitors such as sirolimus. The concern with tacrolimus is kidney toxicity at high levels, which is why drug levels are checked as scheduled.

Can the native kidneys still in the body cause foamy urine?

Yes, early on. Most native kidneys are not removed and may still make protein-containing urine. In 14 living-donor recipients, native-kidney protein fell until UPCR was below 0.2 at an average of 4.5 weeks. After that, if protein is still leaking, the doctor looks for a cause in the new kidney.

How much water should you drink after a kidney transplant?

Drink the amount the transplant center sets, because it depends on body weight, new-kidney function, the heart and the weather. Aim for pale yellow urine. With diarrhea, vomiting or heavy sweating, tell the center the same day, because dehydration and shifting tacrolimus levels affect the new kidney.

What are the symptoms of kidney rejection?

Most rejection has no symptoms and is found by a rising creatinine, so scheduled blood tests matter more than watching foam. Possible symptoms are fever, less urine, swelling, fast weight gain, higher blood pressure or pain over the new kidney. If any of these appear, contact the transplant center now.

How can family help a kidney transplant recipient in the first 3 months?

Help organize medicines and set alarms so anti-rejection drugs are taken on time, log weight, blood pressure, temperature and urine output daily, go along to scheduled blood tests, check with the transplant team before giving any medicine, herb, pomelo or grapefruit, and write down questions for the next visit, such as the latest UPCR value.

Scientific Mechanism

How foam forms and lasts: when the urine stream hits the water surface, air is pulled in as bubbles. Each bubble is wrapped in a thin liquid film. Without something to stabilize that film, liquid drains away and the bubble pops quickly.
Proteins such as albumin are natural surfactants that line up at the film surface and make foam last longer. How much protein is needed before the difference is visible has not been clearly defined
(Khitan 2019).

Where protein comes from after a transplant: tubules injured by low blood flow during surgery, rejection or drug toxicity reabsorb small proteins poorly, producing tubular protein leak.
Filter units damaged by a returning original kidney disease, a new glomerular disease or chronic rejection let albumin and larger proteins through, producing glomerular protein leak
(Ponticelli 2012).

Anti-rejection drugs and kidney blood vessels: calcineurin inhibitors raise vessel-constricting signals and reduce vessel-relaxing signals, so the incoming arteriole narrows and filter pressure and filtration rate fall
(Naesens 2009).
mTOR inhibitors interfere with podocytes, the cells that act as the protein sieve, which is why they are more linked to protein leak
(Diekmann 2012).

Written and reviewed by Asst. Prof. Dr. Norawit Raatpiboon

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