QUESTION: hi,i am 80 years old and my kidneys because of my age are probably off by 40%i never had protein in urine.if I take 8oz of prune juice 2 times a week,will this effect my kidneys?my potassium level was 3.9

ANSWER: Hi Howard,
A potassium level of 3.9(mmol/L) is good. Levels which lie below 3.5 or above 5.0 are unsafe.  Have you been drinking this amount of prune juice regularly?  And is this recent potassium level of 3.9 a true reflection of your prune juice intake?  If it is, then all is fine.  You may already know that prunes (and prune juice) have a high potassium content.  When kidneys are not functioning at their optimum (which occurs naturally with age), potassium may not be filtered and cleared as effectively.  The result being a potentially raised level of potassium.  High potassium levels (or 'hyperkalaemia') can give rise to vague, generalised symptoms such as weakness, and muscle aches.  Cardiac arrhythmias are a serious and potentially life threatening complication of high potassium.  

References suggest that our daily potassium intake should be in the order of 4700mg, but for those with moderate renal impairment, intake should be reduced to half this amount. 8 oz (roughly a cup) may have 500mg or more of potassium.  So, having 2 cups a week should be fine.  The key is to observe your other sources of potassium, and then calculate your total daily intake.  It may be a question of compromise eg, have your prune juice, but limit other sources of potassium eg, avoid banana on those days.

I have included some links below that list the potassium contents of foods.  This may help you calculate your total daily potassium intake (and that of other minerals, such as phosphorus and sodium).

In any case, it's always important to have your regular urea and electrolytes blood tests.  This test investigates your potassium level and kidney function.  You may be required to have this every 3-6months, or more frequently if levels are unstable.

I hope this helps, Howard.  All the best.

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QUESTION: perhaps I   should take lactulose,it doed not effect kidneys and few side effects,the only question is does it raise blood sugar in diabetes,some reports say it does wiakeepidia says lactulose stays in colon and has no effect on blood sudar.the other day I took  3teaspoons of lactulose and had eight bowel movements.maybe I should cut it down to teaspoons instead of 3.can you take it when you are constipated then daily?think I should with 2 glasses of prune juice a week rather then take lactuloseat 80 years of age,no protein in urine and gfr 51i think I just have aged kidneys.sorry to write tou this much but the doctore are internist told me to take miralax a kidney killer

Hi Howard,
Lactulose is poorly absorbed from the intestines, and at normal doses, it is unlikely to have an effect on blood sugar levels.  It is, therefore, not contra-indicated in diabetics.  Because it has negligible systemic absorption, it is unlikely to have an effect in kidney function either.  Lactulose is metabolised by colonic bacteria to produce byproducts that go on to exert an osmotic effect within the gut lumen (ie. draw fluid into the intestine).  It is important to keep up your fluid intake.

Yes, it can be taken for constipation and then daily thereafter.  Although proper diet/fluid intake and fibre supplements are always regarded as first-line.  The dose initially is 1545 mL daily in 1 or 2 doses.  The onset of action is usually around 1-3 days.  Then as a maintenance dose of 1530 mL daily.  It would make a a suitable alternative to prune juice.  You are probably already aware that lactulose is very sweet.  It can always be mixed with water or even milk to help disguise this taste.

All the best, Howard.  No worries about the questions.  I am always happy to help.  


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Gisella Campanelli


I am able to answer questions relating to pharmaceuticals, therapeutic regimes and primary health care. This includes offering advice on drug indications, dosages, and disease state management. I can also identify side effects, drug interactions and contra-indications, and offer recommendations on ways to mitigate these. I can diagnose minor illnesses and suggest appropriate over-the-counter remedies and/or preventive healthcare tips. I can recognize cardinal symptoms which would otherwise require referral to a medical practitioner.


I am a registered pharmacist in Australia, and I have practiced in a hospital pharmacy for over thirteen years. My clinical specializations lie within the areas of psychiatry and general medicine (including gastroenterology, respiratory, endocrinology, neurology, infectious diseases, gerontology, dermatology). I self-managed the training program for pharmacy interns in preparation for their final registration exams, and I have worked for the Pharmacy Board of Australia as an examiner and exam writer.

I hold a Bachelor of Pharmacy from the Victorian College of Pharmacy, Monash University, and I am board-registered to practice within Australia. I also hold a Master's degree in an unrelated field (art conservation).

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