Potassium is a very important electrolyte in a cat's diet. It supports normal muscle function, including that of the heart, and plays a role in nervous system function. It also helps maintain acid-base balance. Impaired kidney function can lead to either a deficiency or an excess of this mineral in the body.
What does potassium do?
Maintaining an appropriate potassium level in the body is essential for normal muscle function. This is related to its role in maintaining the proper membrane potential of cells. Potassium also affects nerve impulse conduction, which is important for a regular heart rhythm. More specifically, it is involved in the function of the sodium-potassium pump. By supporting smooth muscle function, potassium helps maintain intestinal motility. It also contributes to acid-base balance. Among other reasons, this is why any abnormality in the body's potassium concentration may be associated with kidney disease. If a cat's diet contains too little potassium, or if the cat receives excessively large volumes of intravenous fluids, hypokalaemia—that is, an abnormally low blood potassium level—may develop. An elevated potassium level is called hyperkalaemia. It is very often associated with urinary tract obstruction, which requires treatment as quickly as possible. Otherwise, it may become life-threatening. In a healthy animal, excess potassium is excreted in the urine, so its level can rise when various problems interfere with urination.
Hypokalaemia
Increased urinary potassium loss, chronic kidney disease, or inadequate food intake can cause the blood potassium concentration to fall too low. Signs may include lethargy, reduced appetite, and difficulty moving due to impaired muscle function. A lowered head and downward flexion of the neck are common. Impaired smooth muscle function may also cause gastrointestinal motility problems, such as constipation. If these signs occur, it is best to arrange a clinical examination and blood tests recommended by a veterinarian as soon as possible, because many of them may also be associated with other disorders and are not all specific to hypokalaemia.
Hyperkalaemia
An elevated blood potassium concentration most often results from urinary tract obstruction, but it can also be caused by a ruptured urinary bladder. Signs may include lethargy, muscle weakness, and an abnormal heart rhythm, which is a serious warning sign requiring thorough diagnostic tests and prompt treatment.
Potassium in a BARF diet
Potassium deficiency is one of the issues frequently highlighted in studies of BARF diets. Potassium occurs naturally in skeletal muscle meat, especially beef, poultry, and fish, as well as in some organs, such as the heart. When formulating a diet, it is advisable to refer to FEDIAF nutritional guidelines. You should not assume that feeding meat—even though it contains potassium—automatically meets a cat's daily requirement for this mineral. Conversely, potassium supplements should not be given without first accurately calculating the diet's potassium content and determining the individual cat's requirement. Requirements differ between healthy and ill cats, particularly those with urinary tract disease. Some medications also affect potassium levels in the body. Cats with health conditions therefore need regular monitoring of their blood potassium concentration, even when the amount supplied by the diet meets their calculated requirement. It is worth remembering that potassium is water-soluble, so discarding meat juices—for example, the liquid released during thawing—causes at least some potassium to be lost.
Sources:
- Dow, S. W., Fettman, M. J., Smith, K. R., Hamar, D. W., Nagode, L. A., Refsal, K. R., & Wilke, W. L. (1990). Effects of dietary acidification and potassium depletion on acid-base balance, mineral metabolism and renal function in adult cats. The Journal of Nutrition, 120(6), 569–578. https://doi.org/10.1093/jn/120.6.569
- National Research Council (2006). Nutrient Requirements of Dogs and Cats. National Academies Press. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
- Dow SW, LeCouteur RA, Fettman MJ, Spurgeon TL (1987). Potassium depletion in cats: hypokalemic polymyopathy. JAVMA 191(12). https://pubmed.ncbi.nlm.nih.gov/3693009/
- MSD (Merck) Veterinary Manual. Overview of Disorders of Potassium Metabolism in Animals. https://www.msdvetmanual.com/metabolic-disorders/disorders-of-potassium-metabolism/overview-of-disorders-of-potassium-metabolism-in-animals