Can Lactulose Increase A Cat's Water Intake? My Cat Takes 4ml Of Lactulose Daily For Constipation.


2 Answers

Anonymous Profile
Anonymous answered
I'm sure you've figured out the problem with your cat but for anyone else with this problem with their cat there is additional information to be known. Longterm use of lactulose seems to cause hypercalcemia in cats. A symptom of hypercalcemia is increased water intake among other things. Chronic constipation in a cat is sometimes hard to treat and lactulose is wonderful in curing that problem. But hypercalcemia is not good for many reasons including the formation of calcium oxalate bladder stones which is only treatable via surgery. Miralax works, in my opinion, better than lactulose with no side affects. You'll fing you have to administer it less often too. Also it's over the counter. Ask your vet to run a total body function blood test. If the calcium is increased they will suggest doing a PTH and ionized calcium blood tests as well. Just discontinue the lactulose and use something else and retest in a month. Most vets will say hypercalcemia is not a side affect of lactulose. There have been studies with lab rats but none with cats so there is no clinical evidence to date. It does seem to be a common Tre d among chronic constpated cat owners however. Explore these options and good luck to anyone in need of this information.
Jessica Smith Profile
Jessica Smith answered
Polydipsia (increased drinking) secondary to polyuria (increased urination) is a common sign of diabetes.  Diabetes causes the urine to become very dilute.  This increased loss of water from the body stimulates thirst and therefore an increase in water intake. 
Lactulose is an osmotic laxative.  It works by increasing the amount of water content in the lower intestine by drawing moisture through the walls of the intestine.  This softens the stools and makes them easier to pass.  In this regard, Lactulose is causing your cat to excrete more water in its faeces, so it may be affecting your cat’s thirst.
Lactulose can also cause blood sugar levels to rise.  For this reason it is advised that lactulose be used with caution in humans with diabetes, as blood sugar in those individuals must be carefully controlled. 
I think it is the diabetes which is primarily causing the increase in water consumption, but the lactulose may not be helping things.  I would advise you to discuss it with your vet.
thanked the writer.
Anonymous commented
Thanks for the really detailed answer. It is a big help.

When I said I was taking my cat to the vet to check for diabetes it is not because she has it (as far as her recent blood tests show), but because I was so freaked by her increased water intake and increased urination that I want to discuss the whole thing with my vet.

Based on your explanation, Lactulose is probably the culprit..

I also checked with a very good pet store near me and they said that Yes, Lactulose does increase drinking water in cats.

I will be retrying some fine ground psyllium too..

Thanks very much.


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