MePhysicians can only do so much with stone prevention because a large part of the work can only be done by patients themselves.

The Five Steps to Stone Prevention, the two articles on how to read your 24 hour laboratory reports for calcium and uric acid stones, and the article on how to be a successful kidney stone patient are the reference materials you need to accomplish your part of your personal stone prevention program.

It is now time to pull these four articles together into an organized approach that any patient can follow.


Before your visit to decide on prevention Read the article on how to be a successful kidney stone patient, where  you will find lists of materials to bring with you. 

Know your stone type(s).

Get the right blood and 24 hour urine testing.

Read your own 24 hour urine laboratory reports and make notes so you will be fully prepared to make use of what your physician knows

Perform what I call the ‘Great Integration’ and have it ready as a key part of your discussion with your physician.


How, exactly, do you prevent what you do not know?

Stone analysis is the foundation of your prevention.

Find past analyses. If you have stones in your possession, get them analyzed.

If there never have been any analyses and you have no stones, make a good guess. Part 1 of Five Steps details an approach, so read it now if you do not know your stones.

Do not give up easily. Someone, somewhere, may have your report. If all you can do is guess, guess as best you can. Have your physician guess, too.


The needed blood tests can be obtained from any certified laboratory. Be sure they are fasting.

Proper 24 hour urine testing is best done through one of the national vendors of such products. Local hospital laboratories are not ideal and often simply send the urine out to such vendors with high possibility of adding errors. Vendors provide home collection and mailback materials, and issue a graphic and complete report of all measurements including supersaturations.

Much of the value of your 24 hour testing is determined by your behavior. You need to collect so the results reflect your average life conditions. If you show off and drink a lot, you will be fooling yourself. If you collect only on a weekend day, likewise. Two collections are much more valuable than one. If a collection goes badly – loss of a sample, uncertain timing, throw it out and do another – it costs nothing and prevents mistakes.

You are the one who times your collections. Make a copy of your start and stop times, so you can compare your results to those in the final report. Sometimes there is a mistake in transcribing.

You will measure the urine volume in many cases, or can measure it from markings on the container. Write them down in case there is a question of errors. The largest vendors, Litholink (a branch of LabCorp) and Quest actually infer the 24 hour urine volume and do not use your measurements in most cases. They add one or another proprietary marker to the collection container and measure its concentration. This latter tells them the volume in which the material has been diluted. That volume is the 24 hour urine volume. Here and there, though, if you have measured carefully your measurements may help resolve problems when the multiple samples from you fail to match in their completeness of collection. For your measurements to be useful, you need to read the volume as precisely as possible – get as specific a reading from the measuring scale as you can – and write the results down.


As I launch into this I want to make clear my intent is to enable patients to make the best use of their physician visits. You need a physician, but you can do a lot before the visit to become thoughtfully informed and thereby be a more useful partner. If you have thought through your own information the time you have together can be used for more detailed explanation and less for routine matters you can do beforehand for yourself.


Find the 24 hour urine creatinine excretions and see if they match within about 15 percent. If not, one is wrong. Recheck your timings. If you think the urines were perfect, call the vendor and check their times and volumes. If times and volumes match and the creatinines do not match you probably have made a mistake and you should get a third as a tiebreaker before going to your physician.


Abnormal means the 24 hour value is known to be associated with risk of stones. Mostly the associations are from prospective observations. Some are based on very firm physical chemistry. The following is directly from the two articles on reading 24 hour urines for calcium or uric acid stone risk.

Write down each of the following that is abnormal – this is your list of abnormalities that are candidates for treatment

Urine Volume below 2 liters per day is abnormal – low flow

Urine calcium above 200 milligrams per day is abnormal – called hypercalciuria

Urine oxalate above 35 mg per day – called hyperoxaluria. (Strictly speaking, values above 25 mg per day are abnormal in that an association with stones can be detected above it. But most people indeed excrete more than 25 mg of oxalate, so a more practical level is above 35 mg per day).  Hyperoxaluria is almost always due to a high diet oxalate intake, low calcium diet intake, or both. Values above 80 mg per day are very unusual and may reflect a systemic disease – your physician will note this – be sure it is discussed.

Urine citrate below 400 mg per day is abnormal – called hypocitraturia.

Urine pH below 5.5 confers a risk of uric acid stones – low urine pH

Urine pH above 6.3 confers a risk of calcium phosphate stones – high urine pH

Urine sodium above 100 mEq per day is above the recommended for US population – high sodium intake

Urine sodium above 65 mEq per day is above the optimal intake for the US population – above optimal sodium intake


Supersaturations are not compared to normal or to stone risk because we lack the critical information. But we know one thing: If you are forming new stones, the supersaturations for the crystals in your stones are too high and need to be lowered.


Here it is, and you are ready.

This is a breakdown of what is already said in another article.



Think about it and make your own decision. When you see your physician, he or she will read your scans with you and count if stones are increasing or decreasing in your kidneys. You will have gathered all your old records and will know when stones have passed or were removed. Your physician may have more such information. Decide if new stones are indeed forming.


We have been here before – most critical to know.


Write them down; these are your relevant supersaturations


This can be confusing so lets review things.

The purpose is to lower by half or more the supersaturations in your urine related to the crystal(s) in your stones. If your stones are mostly calcium oxalate then calcium oxalate supersaturation is your main target. If your stones are mainly calcium phosphate then calcium phosphate supersaturation is your main target.


Correct abnormal urine volume, calcium, oxalate and citrate in that order or priority. For calcium I have linked to idiopathic hypercalciuria, being the usual cause, and that will link to diet sodium and diet sugar as factors your can correct without medications. If your sodium is above optimal (see above) lower it. If you eat lots of sugar, stop. Then, when fluids and diet are both corrected recheck. If CaOx SS has fallen by half or more that may be enough. In principle you could wait and see if stones are now prevented – time will tell.

I am not saying that you treat yourself nor that this is an approach written in stone. I am saying this is a common strategy that your physician may well want to use. There may be reasons not to: You have had too many stones; you have only one kidney; risk to your general health of any more stones is really high.

Thiazide diuretics are a next step when fluids and diet have failed to lower supersaturation enough or new stones form. They should usually not be a first step but rather when follow up 24 hour urines demonstrate that urine supersaturation has not fallen by half or, if it has, if observation shows you that new stones are still forming. Potassium citrate is like thiazide as it will lower urine calcium – not as dramatically – and lower supersaturation by binding calcium, as well as inhibit crystallization. But this agent has become expensive, and is always hard to take because pills are big. So thiazide is a more common first drug.


Correct abnormal urine volume, calcium, pH, and citrate in that order of priority. High volume (above 2.5 liters) is a very useful step here because it can be sufficient in some cases. Calcium is as for calcium oxalate: reduced sodium and sugars, thiazide diuretics is needed when diet and fluids have failed. Urine pH elevation in calcium phosphate stone formers is usually innate and not directly amenable to change but there are odd situations where this is not true. Sometimes people take in very large amounts of fruits – especially smoothies – compared to proteins and have an alkaline diet. One can try rearranging things if you are like this. Potassium citrate is an uncertain treatment here because no trials have been done for calcium phosphate stone formers.


Correct abnormal urine pH and volume in that order of priority. This is the easy one – raise the urine pH, almost always with potassium citrate or other alkali formulationsWhatever uric acid has been forming will form no longer, and some may dissolve.


This is not for you to figure out.

A good screening table is in Five Steps. It requires blood and 24 hour urine measurements and a physician to interpret them. Do not try to figure this one out yourself – it is not wise nor is it practical or safe. Most stone formers do not have such diseases but those who do are in a different realm than the rest. Sites like this one, even though medically rigorous, cannot guide patients with these diseases but only inform them.

The table is not comprehensive nor meant to be. It is a table of highlights. I know many more rare and obscure causes, and so do your physicians.

By all odds you do not have any of the diseases. But do not assume.

Be sure with your physician.

If you have a systemic disease, much of the foregoing will become subsumed in systemic treatments, and these are beyond what we can do here.


Between Five Steps, How to be a Successful Stone Patient, and the articles on reading your reports you are ready to do your best when you see your physician. You should expect to leave with mainly lifestyle and diet changes after a first visit, and plans for a follow up with labs in a month or two. Every cycle is the same, however, until you have reached your supersaturation goals and stones no longer form.

I hope these articles help you achieve what we all want. Let me know. Write a comment. Being only electrons, these articles can be reshaped any time, but it is really patients who can tell me how best to do that.


  1. Rob Lewis

    Hi Dr. Coe,

    Many thanks for your detailed kidney stone information! So many other sites simply suggest that one should drink a six pack of Coca-Cola and down a cup of pureed asparagus! One and done!
    I’m taking a stone in for analysis tomorrow and plan to discuss my current situation with the urologist. Long story short, is it possible that a 2 month work-out and protein (meat and protein shakes) binge could have precipitated a recent bout with stones? I’m 46 and have never had a problem until 2 weeks ago. Is it possible NOT to have had gout but to now have uric acid kidney stones? Drinking lots of water with lemon, aloe vera juice for ureteral irritation, flo-max for max output, and some baking soda and apple cider vinegar here and there.

    Many thanks,
    Rob Lewis
    Raleigh, NC

  2. Angela

    Dr. Coe,
    I am writing today with a lot of frustration. I was diagnosed with a 5mm kidney stone in April that was in my kidney. The ER referred to a urologist. Upon my visit to urologist, I was told it is difficult to pass that size, but given a week to pass it with a prescription of Flomax. In a week, I had not passed the stone and they scheduled me for lipotripsy. Since the surgery, I have felt worse. I went back, they did another ctscan and said it was now a 2mm in my ureter tube near bladder. It is now June and I am really feeling worse. The urologist sent me for a ultrasound yesterday because I still have blood in my urine also. I discovered at the ultrasound the urologist never told me all the ct results because I still have a 5mm in my kidney as well as the 2mm. I have been reading over the last several weeks and found so many recommendations to drink lemon water. I have been doing that very frequently; of course, in hopes of dissolving the stone. Today, I found your site. I have never once had the urologist recommend blood or 24 hour urine test. I do not know what kind of stone I have. I cannot understand why it would be taking this long to pass it and if all my pain and discomfort is actually just from a stone. After reading several of your articles about oxalate, I am now concerned the lemon water may have been adding to my problem. I have been wondering if these stones could be caused from a green smoothie health kick I had been doing for 2 months prior to the first onset of problems. All this being said, I don’t know what to do from here. I do not feel like I am getting anywhere with the current physician. I do not want to do the lipotripsy again. I am open to diet change, but I don’t even know if it is an oxalate stone. Does the physician have to order this 24 hour urine test? Thank you for any information and help!

    • Fredric Coe, MD

      Hi Angela, I am sorry for all your problems. Your physicians are indeed essential but most evaluate and treat stone formers. The article you commented on is indeed a gateway article into stone prevention and links into Five Steps etc. I would begin to use it to plan your evaluation and help your physicians get it done. Please to not go about finding remedies at random, but follow the plan. Here is perhaps a helpful other article that is just getting finished. Your smoothies might have been culprits but frankly those destined for stones are vulnerable to many kinds of stresses other people shrug off. Regards, Fred Coe

  3. Lee

    Dr. Coe,
    When I had a stone last year that required a ureteroscopy (it was stuck in the ureter and was 90% calcium oxalate/10% uric acid), another stone showed up in the CT scan that was 5cm.. I was told it was in the kidney and may stay there indefinitely without causing a problem, unless it grows. Once a stone is already there, is there anything I can do to prevent it from becoming dislodged and traveling down the ureter? If it’s another calcium stone, do they ever get smaller or dissolve on their own or even disappear, or is there anything that can be done to get rid of it, short of a ureteroscopy? It’s like walking around with a loaded gun, never knowing ifor when it’s going to go off… very unnerving. Thanks

    • Lee

      If my post gets read, I meant to say 5mm, not 5cm.

    • Fredric Coe, MD

      Hi Lee, Calcium oxalate stones do not dissolve. The uric acid portion – if the stone has any – will dissolve with increased urine pH. You should have your physicians monitor growth of the stone, and also be wary of pain or bleeding that might signify the stone has obstructed. Whether it is free in the renal pelvis or attached on to the kidney also matters. From here, only generalities, I am afraid; one needs to see the CT scan, and make judgments only your physicians can make. OF real importance, you should have a proper prevention program because more may form. Here is a good introduction. Regards, Fred Coe

  4. irfan bashir

    hi doctor,
    I have been facing kidney stones for the last 20 years. Every ear I have stones of multiple origin expelled by litholapaxy or herbal medicines or ESWL.
    I just did the 24H urine test with abnormal urine citrate of 2.21 mg. with all other tests being clear.
    my age is 40 years now and the urologist advised urocit-k 10mEq b.i.d , which I took for 3 months. After stopping the medication, I again develpoed stone. Please give me your advice.

  5. Lisa Baker

    Oh and I was diagnosed with osteopenia last year with first bone density test….

  6. Lisa Baker

    Thank you for this wonderful resource! I recently passed a 4MM stone left kidney (1st one). The CT from ER visit revealed another 4 MM in left kidney and 4 smaller stones. The analysis of the stone I was told was 95% calcium oxalate.

    A subsequent KUB 2 weeks later as result of miserable back and left side pain revealed only the 4 MM and did not detect other stones. The pain subsided after about a week, but I have no confirmation of passing another stone or the cause of pain. My 24 hour urine results are:
    Urine Calcium 244
    Urine Sodium 171
    Urine Oxalate 34
    Urine Citrate 764
    Urine PH 6.977
    Urine Volume 1.71

    My urologist’s P.A. suggests increase in water, decrease salt and ordered another KUB and urinalysis with C&S if indicated, in 3 months.

    After absorbing information from this site, I’m thinking that I should have another 24 hour urine, perhaps request along with the other 3 month tests. I’m also wondering about the oxalate and PH and if they indicate measures of prevention outside of limiting sodium and increasing volume. Lastly, it was mentioned that 4MM is borderline for lithotripsy. Of course, no one wants to pass a stone but I don’t know much about this procedure and when it makes sense. Your comments are appreciated!

    • Fredric Coe, MD

      Hi Lisa, I gather you have a calcium oxalate stone and your urine values indicate hypercalciuria, high sodium intake, high pH and fair urine volume. I agree with the low sodium, and a good goal is 1500 -2000 mg, lower is better. Likewise, since you have bone disease – your second comment – and hypercalciuria you need 1200 mg of calcium. That high calcium diet will lower your urine oxalate all by itself, and the low sodium intake will keep the urine calcium from rising with the higher calcium intake. Here is an article on that three way approach. The high urine pH is not of obvious cause, but the stone is CaOx not calcium phosphate so leave this alone right now. By all means get a follow up 24 hour urine and be sure the sodium is down, the oxalate is down, the volume is up and the urine calcium is no higher. Regards, Fred Coe

  7. Frank

    I had a first calcium oxalate stone 4 years ago. Then another one that got removed through surgery in October.
    Both stones were about 6 mm big.
    I just did the 24H urine test.
    ” Only” the following results are outside the recommended ranges:
    – citrate: 160 mg
    – magnesium: 44 mg
    – potassium: 17.
    I have been adding a small spoon of pure lemon juice into each glass of water that I drink, and I drink 6 to 10 large glass of water per day.
    What treatment would you recommend to prevent recurrence ?

  8. Adam

    Hello, I was just wondering if you could either clarify for me or break down the options a little bit more. I have had 3 kidney stones. The last stone was calcium oxalate. My serum calcium number is 9.6. My Urine Citrate 249mg per day. My urine calcium 351 mg per day. You mention “Correct abnormal urine volume, calcium, oxalate and citrate in that order or priority”. Urine volume seems obvious to fix, increase water intake. How ever correcting abnormal levels of calcium, not as obvious for me. oxalates I would assume could be corrected with diet modification. Then finally citrate I am guessing also would be diet based like lemonade, and potassium citrate supplements. Any further you can help me understand different options to correcting those areas would be appreciated. Thanks for your time,


    • Fredric Coe, MD

      Hi Adam, Thanks for the question. So, you have your crystals – calcium oxalate, and you have your abnormalities: citrate calcium and although I do not see a volume presumably that as well. You correctly note that fixing volume is simple enough – though burdensome in reality. Remember the goal is to lower the urine supersaturation with respect to the crystals, which for calcium oxalate means that supersaturation. You do not mention an abnormal urine oxalate, so I guess that is not present.

      The text reads: ‘Correct abnormal urine volume, calcium, oxalate and citrate in that order or priority. For calcium I have linked to idiopathic hypercalciuria, being the usual cause, and that will link to sodium and sugar as factors. Thiazide diuretics are a next step when fluids and diet have failed. They should not be a first step but rather when follow up 24 hour urines demonstrate that urine supersaturation has not fallen by half or, if it has, if observation shows you that new stones are still forming.’ So with water I would lower urine sodium and diet sugar and see if urine supersaturation has fallen by half. If so, and if stones are not highly frequent, I often wait to see if that is enough. If not, then thiazide.

      Also, I did not mean you are to be all by yourself. Your physician can certainly help a lot. But the intent of the article is to prepare patients to get the most out of the physicians who care for them.

      Your question is so important I have edited the article to make these points clearer than they are now. Much thanks, Fred

    • GULREZ KHAN ("Gus")

      Hello doc,

      I live in Texas. I am a 36 years old male. I am 5.7 tall and weigh 150 pounds. I mean, I am in a great shape. However, 2 weeks ago I passed a calcium kidney stone. My PCP told me to check online about the dietary recommendations after having a calcium kidney stone. Believe me, the research for a near perfect diet for this is more frustrating than having a kidney stone. Every sources tells a completely different story. I am tired of researching due to varying perspective.

      So, you tell me what do I eat and drink and what not? I am exhausted of looking at oxalate, low oxalate , high oxalate, and all this crap.


      • Fredric Coe, MD

        Hi Gus, You are reading the article I wrote about what to do. It does not really make much of oxalate but rather that you need to know why the stones form in order to prevent them. First, what is the stone? Calcium goes with another name like oxalate or phosphate and that matters. Second has your physician looked for and excluded systemic diseases as a cause? Third, you need 24 hour urine testing: WHat is causing stones of the kind you formed? There are no varying perspectives about what I just wrote: Every responsible physician will agree these three steps are needed. Once you know what is wrong diet or even meds can be figured out. Without these basics, no one can tell you what will work. In general, assuming you have the common calcium oxalate stone and no systemic diseases, the ideal kidney stone diet is more or less the modern ideal US diet; take a look. Regards, Fred Coe

  9. Ed Smith

    Hi, what is the oxalate content of lentils?

    • jharris

      Hi Ed.

      Don’t have a known source, but from all my readings, I think they tend to run on the higher side. I would have them in small portions.


  10. Tonya Blaine

    i have had 2 kidney stone surgeries in 2 yrs…. I had a 24 hr urine done with the following results;
    are these results normal

    • Fredric Coe, MD

      Hi Tonya, I guess there is not enough information to say. What were the stones made of? For example were their crystals calcium oxalate, or calcium phosphate, or uric acid or some mixture. Was the urine collected representative of your normal life as was led when you formed stones? Let me know and I will try to help. There is no such thing as a normal supersaturation value, it is that the supersaturation in the urine of someone who is forming new stones is too high in relation to the crystals in the stones formed. Take a look at this video. Regards, Fred Coe


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