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. Andrea Zappia

    Hi Dr. Coe, My daughter is 16 yrs. old. She just passed a kidney stone on (Feb. 19th, 2018) (My husband passed his second stone in December 2017. He has calcium oxalate stones and his look entirely different than the one my daughter passed.) Hers is a whitish color and has a rusty looking spot on it and very jagged looking all over and in a rectangular shape, whereas my husbands is dark and not so jagged at all. I am planning on having hers analyzed to see the type of stone it is.
    My concern is how young she is and already having a kidney stone. We live in northern indiana by Nortre Dame and see that you are located in Chicago. Would it be a good idea to see you since she is so young and already has passed a kidney stone? (Kidney stones run in husbands family) In the meantime I plan on looking at your website to find as much information as I can. Thank you for your time.

    • Fredric Coe, MD

      Hi Andrea, In fact with a husband and daughter with stones, and given your location, you might just do as well coming to the UC where I or a colleague can just get the evaluation done and treatment started. I wish to make clear that I am paid as a professor and derive no financial incentives from medical practice and so feel free to make this recommendation. My secretary is Kathleen Dineen, 773 702 1475. Regards, Fred Coe

  2. Karen

    Hi Dr. Coe,
    I have had four kidney removed in the last twenty years. I take potassium citrate twice daily. My urologist had me do another 48 hour urine collection which was both days was over 400 in calcium. He wanted me to see an endocrinologist for possible hyper parathyroid. I contacted Norman Parathyroid Center in Florida because they do so many of the surgeries. They don’t think that I have it but rather renal calcium leak, which they don’t treat. My PTH intact was 71pg, my calcium ionized serum was 1.32 mmlo/L, my calcium was 9.7mg and my vitamin D was 34ng. My sodium is 141 which my urologist said to reduce, which surprised me, because I watch my salt intake very carefully. After I read the symptoms of a hyper parathyroid, I was sure that was the problem because I have so many of the symptoms. I am so tired, my legs have hurt so bad for the past year, I have such bad headaches, am forgetful and just crabby . I have gained a lot of weight, but am not sure if it’s because of my legs and hips always hurting. I just feel lousy for about a year. I don’t know who to see next. Would I come to your practice or do I see an endocrinologist. Any advice would be appreciated. Thank you.

    • Fredric Coe, MD

      Hi Karen, You have normal blood calcium and high urine calcium, and if the former is always the case in properly drawn samples, fasting, primary hyperparathyroidism is not present. I can certainly see you if you can come to Chicago. But I imagine the problem is idiopathic hypercalciuria, easily treated. The high PTH may be low calcium diet, a very bad idea indeed. You would need a high calcium low sodium diet. Let me know, Regards, Fred Coe

      • Karen

        Dr. Coe,
        Thanks for your reply. I live in Chicago. I do have a very low calcium diet. I have looked at my salt intake and think it’s low but might have to make it lower. Is there a general diet to follow for this that would help. Also, would adding calcium help with the bad leg cramps that I have daily?

        • Fredric Coe, MD

          HI Karen, If you are in Chicago the easiest would be to just come to see me and get real advice based on a proper knowledge. Adding calcium has many purposes, and I would be better for you in person. Regards, Fred Coe

  3. Steven Crays

    Hello, Dr. Coe.
    I had one 2mm stone back in 2008 and another 4mm stone last year in 2016, both originating in the right kidney. Unfortunately, I passed both without being able to capture the stones for analysis. My second episode took 2 months for the stone to finally pass being lodged at a point just before the bladder. Reflecting on my past dietary habits, my fluid intake was lower than suggested and my oxalate intake was very high so I am making the big assumption that the stones were CaOx.

    I really wanted to take a moment to thank you for your work. Moving forward, I will heed all of your advice. The one question I have is, why is there so much discrepancy out there with regard to the level of oxalate in foods? Is it the method of testing? One resource will say coffee is higher in oxalate and another will say it’s low. Because of your incredibly informative website and scientific approach to managing kidney stone formation, I plan to use your information over other resources. Thanks, again. All the best. Steve

    • Fredric Coe, MD

      Hi Steve, I do not know why the lists vary so. Our list originated in the Harvard School of Public Health. Prof Ross Holmes, who really is a food oxalate expert, curated the list and corrected as necessary. He is aware of the many conflicting lists, and thinks they are just old errors. Regards, Fred Coe


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