Pet Factsheets

Hypocalcemia and hypercalcemia

Hypo- and hypercalcemia can both cause illness in rabbits. A lack of, or too much calcium in the blood, is likely to be a sign of another disease process so your rabbit will need veterinary attention and further treatment. Calcium is an essential part of a rabbit’s diet.

Hypocalcemia is defined as low blood calcium.

Hypercalcemia is high levels of calcium in the blood. Normal blood levels of calcium for rabbits are 2.2-3.9mmol/l. However, calcium levels will rise after the rabbit has eaten foods containing calcium, so a snapshot blood test needs to be interpreted carefully.

Calcium is essential.

As with other mammals, calcium is required for healthy muscle and nerve function, and also to ensure strong and healthy bones and teeth.

Rabbit’s teeth grow throughout life. Their incisors (front teeth) grow around 2-3mm per week and their molar (back teeth) grow 2-3mm per month. All of this requires a constant supply of calcium to ensure the teeth remain healthy.

Rabbits are fairly unique in the way that they metabolise calcium. The vast majority of mammals will only absorb the amount of calcium that they require from their diet and excrete less than 2% through their urinary tract. However, rabbits absorb all the calcium from their diet, relying upon urinary excretion as the major route of getting rid of any excess.

The urinary tract in rabbits is identical to that of other mammals and exists of two kidneys, each with a ureter running from it to the urinary bladder. The urethra is the exit tract from the bladder, which enables the rabbit to pass urine out of their body.

Hypocalcemia is rare in rabbits, which is likely due to their absorption mechanism to ensure that all calcium in the diet is absorbed. Causes may include severe liver failure, insufficient dietary update of calcium, diarrhea and sometimes with late stages of pregnancy and during lactation whereby the amount of calcium required by the rabbit is dramatically increased.

Hypocalcemia may cause twitching, ataxia, seizures and death if the condition is not corrected promptly.

Dental disease is a complicated process in rabbits, and there are many potential causes and factors which play a part. Lack of calcium is thought to be one of these, since the teeth may work loose from their sockets, changing the occlusion angle and the way in which the rabbit chews. This means the rabbit will not wear all the surfaces of the teeth evenly, leading to spurs forming. Horizontal ridges running across the incisor teeth are indicative of a lack of calcium in the teeth.

Hypercalcemia is normally caused by renal failure (secondary hyperparathyroidism), nutritional hyperparathyroidism, lymphoma, thymomas and hypervitaminosis D.

Diets high in calcium, together with other predisposing factors to urinary tract disease, such as obesity, lack of exercise, spinal/hip pain, lack of water consumption, lack of opportunity to urine etc, may also cause hypercalcemia.

Hypercalcemia causes mineralization of the soft tissues, such as kidneys. Stones (uroliths) may also develop anywhere in the urinary tract (kidneys, ureters, bladder and urethra). Stones which block the urine flow from the kidney to the bladder will cause hydronephrosis (enlargement of the kidney). This is extremely painful and serious.

Both conditions are secondary to an underlying cause or more than one cause, so this must be identified and corrected. Rabbits that have developed urinary tract stones will need to have these surgically removed, and the underlying cause/s identified and addressed. This should only be done when the rabbit’s condition has been stabilized.

Rabbits suffering with hypocalcemia caused by pregnancy or lactation need emergency veterinary treatment and calcium supplementation.

The best preventative measure is to ensure your rabbit is fed a suitable diet. This must consist of 85% hay and grass.

Alfalfa hay is high in calcium so should only be fed to very young rabbits and pregnant/lactating female. Other types of hay, such as timothy, brome, oat and meadow hay are suitable for rabbits. Pellets must make up no more than 5% of the diet and exercise by scatter feeding should be encouraged.

Water must always be available in a familiar drinking system – ideally a non-tip water bowl as rabbits generally prefer a bowl over a bottle and bottles often freeze in winter or jam, meaning the rabbit may go several hours without access to water.

Do not allow your rabbit to become overweight.

Feeding fresh foods, such as herbs, greens, broccoli, celery, etc should be encouraged each day and make up 10% of the diet. This helps to add fluid to the diet and variety.

Take care with any treats that you offer; these should be healthy and not form a major part of the diet.

Make sure your rabbit has ample room and opportunity to exercise and litter trays are always available, clean and accessible.