This article focuses particularly on tetany associated with hypocalcaemia. However, tremors, muscle twitches and epileptic-type seizures do not all result from calcium deficiency. Poisoning, another metabolic disturbance or brain disease can cause similar symptoms. Their appearance cannot confirm the cause.
When to see a vet urgently
Contact an emergency vet immediately if your cat has:
- severe or continuous muscle cramps or seizures;
- repeated seizures without normal recovery between them;
- difficulty breathing, collapse or reduced consciousness;
- tremors, stiffness or rapidly worsening general health during lactation.
Do not wait to see whether calcium or milk given at home helps. You can find a vet near you.
Overview
Calcium plays a central role in nerve and muscle function and blood clotting. When levels are too low, nerve cells quickly begin functioning abnormally and muscles cramp. Hypocalcaemic tetany can develop as an acute, life-threatening condition or as a symptom of chronic diseases.
Total calcium reported on a blood test and the ionised calcium available to the body are not the same. Some calcium in blood is bound to proteins or other substances. The free fraction important to nerves and muscles is measured separately when a calcium metabolism disorder is suspected.
The total value can change without the biologically active fraction changing proportionally. Kidney disease, for example, can produce a significant difference between results. A low total calcium value alone therefore does not establish the cause of symptomatic tetany, and you should not try to correct it with supplements yourself.
Causes
- postpartum eclampsia in nursing cats, particularly with large litters;
- hypoparathyroidism, a deficiency of parathyroid hormone;
- chronic kidney failure, with disturbed calcium and phosphorus metabolism;
- pancreatitis;
- severe intestinal diseases with impaired nutrient absorption;
- excess phosphorus, for example from an unbalanced diet.
Eclampsia is rare in cats, but possible and urgent. It can also occur before birth, although the demands of milk production are a common association. Always tell your vet about pregnancy, birth and nursing when a mother cat develops tremors or other neuromuscular symptoms.
Kidney disease changes calcium and phosphorus regulation, but not every kidney patient has symptomatic hypocalcaemia. Low calcium associated with kidney disease does not usually cause the same neurological signs as severe parathyroid hormone deficiency. A new seizure in a cat with kidney disease therefore needs separate investigation.
Medicines, supplements and possible toxins also belong in the history. A human phosphate-containing enema can cause dangerous electrolyte disturbances in cats. Do not use one on your cat yourself. If already given, tell your vet the packaging details and administration time immediately.
Risk factors
- nursing cats;
- cats with kidney or gastrointestinal diseases;
- kittens fed an inappropriate diet;
- cats after thyroid or parathyroid surgery.
Belonging to a risk group helps guide investigation, but does not confirm that seizures result from calcium. It is particularly important to report a change in health after neck surgery. The parathyroid glands regulate calcium, and their function is assessed separately from thyroid hormone production.
Typical symptoms
- muscle twitches and fine muscle tremors;
- seizures and whole-body cramps;
- shaking;
- stiff movement and unsteady walking;
- restlessness and vocalisation;
- rapid breathing and heart rate;
- loss of consciousness during severe seizures.
Symptom severity and combinations vary. Your cat may initially be restless or move stiffly before an obvious spasm. Conversely, similar tremors can reflect another disease. Knowing that the diet contains calcium does not rule out a disturbance, because hormones, absorption and excretion also affect blood levels.
Record when a seizure starts, its duration and whether your cat returns to normal. An existing short video taken safely can help describe the symptom. Filming must not delay care, and your cat should not be positioned or handled to provoke an episode.
Complications and consequences
- severe, prolonged seizures;
- muscle and internal organ damage;
- brain damage from oxygen shortage;
- sudden death without treatment.
Prolonged muscle activity and impaired breathing can rapidly strain the body. A symptomatic cat should therefore not wait for a routine appointment or a new diet. Temporary cessation of symptoms also does not rule out a serious cause if episodes recur or general health remains abnormal.
Diagnosis at the vet
- blood tests and electrolytes to identify low calcium and possible phosphorus and magnesium changes;
- blood biochemistry to assess kidney and pancreatic function;
- ultrasound and X-rays to rule out tumours and inflammation;
- hormone testing to assess parathyroid function.
Ionised calcium results are interpreted alongside your cat's condition and other laboratory findings. Glucose and other electrolytes may also be tested because similar symptoms do not always result from calcium. Correct sample handling matters for a reliable result.
Do not try to convert total calcium into an estimate of ionised calcium using an online correction formula. These calculations can mislead, particularly in kidney disease. When needed, free calcium is measured directly so treatment decisions use appropriate information.
Parathyroid hormone is interpreted alongside the calcium level measured at the same time. A hormone result within the reference range does not always establish appropriate regulation. Your vet assesses whether the amount of hormone fits the blood calcium concentration.
Imaging targets the suspected underlying disease. Ultrasound or X-rays alone do not exclude every cause of seizures. The first question is whether there is a treatable metabolic disturbance and whether symptoms or other findings warrant further investigation.
First aid and treatment
Move away objects your cat could hit and reduce noise. Do not try to hold a convulsing cat still by force. Do not put food, drink or tablets in their mouth during a seizure. Call the practice and follow safe transport instructions.
If eclampsia is suspected in a nursing mother, prevent kittens from suckling and contact your vet immediately. This does not mean leaving the kittens without care: warmth and feeding are arranged separately with professional guidance. Give their age and number and details of the mother's food too.
Symptomatic hypocalcaemia may require intravenous calcium. It is given under monitoring because overly rapid administration can cause heart rhythm disturbances. Your vet also treats seizures and other metabolic abnormalities as needed. A supplement given at home does not replace this emergency care.
Ongoing treatment depends on the cause. Some cats need prescribed oral calcium and vitamin D-related treatment, while others mainly need control of the underlying disease. Treatment requirements are not decided solely from the first seizure or one blood value.
Recovery and monitoring
Improving clinical signs are important, but calcium balance may still need monitoring. Follow-up tests and medication reviews are agreed with the practice. Do not increase, stop or combine prescribed products yourself when your cat seems better.
Monitor appetite, drinking, urination, movement and any new tremors. Also report constipation, vomiting, weakness or other changes during treatment. Calcium supplements can affect the use of other medicines, so every prescription and non-prescription product is reviewed at the appointment.
Recovery of a nursing mother also includes planning continued or reduced nursing and kitten nutrition. A temporary improvement alone does not determine what level of demand is safe. Instructions are tailored to the mother and litter.
Prevention
- balanced feeding with enough calcium and vitamin D;
- eclampsia prevention in nursing cats through monitoring diet and health after birth;
- regular investigations for cats with chronic kidney disease or hormonal disorders;
- avoiding unbalanced diets.
Adequate intake does not mean as much calcium or vitamin D as possible. Do not give extra calcium or dairy products just in case to a pregnant or nursing cat eating complete food without assessment. Excess can disrupt regulation, and supplementation needs are individual. A homemade recipe must be balanced for species and life stage.
Important for cat owners
Tetany is dangerous and always indicates a serious disturbance of calcium metabolism. Remember that any seizures and muscle cramps are reasons to go to a vet or emergency vet immediately. Timely diagnosis and correction of calcium levels can save your cat's life.
Nevertheless, a calcium disturbance cannot be diagnosed with certainty from every muscle cramp. Other causes of seizure-like symptoms are investigated, and the need for urgent help is determined by symptoms and general health. Calcium is given when investigations and the clinical situation indicate it.
This article provides general information and does not replace veterinary care. Contact your vet if you notice signs of illness in your cat.
Frequently asked questions
Can tetany be treated by giving a cat milk?
Not safely. Milk does not replace supervised treatment of symptomatic hypocalcaemia, and seizures may have another cause. Put nothing in your cat's mouth during a seizure. Contact your vet immediately.
Does low total calcium always mean a shortage of active calcium?
No. Total calcium can differ from the ionised calcium situation, particularly in an ill animal. Your vet selects the tests needed and interprets values alongside symptoms.
Does every nursing cat need a calcium supplement?
No. Complete nutrition suitable for reproduction is the starting point. Extra calcium is used only according to need and a professional plan. Tremors or stiffness in the mother are reasons for examination, rather than trying an extra amount yourself.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Disorders of the Parathyroid Glands and of Calcium Metabolism in Cats, Merck Veterinary Manual, accessed 2026-11-05.
- Eclampsia in Cats, VCA Animal Hospitals, accessed 2026-11-05.
- Calcium Supplements, VCA Animal Hospitals, accessed 2026-11-05.
- Calcium Disorders, Michigan State University Veterinary Diagnostic Laboratory, accessed 2026-11-05.
- Epileptic seizures in cats: practical approaches to diagnosis, Journal of Feline Medicine and Surgery, accessed 2026-11-05.
- Cat First Aid, Cats Protection, accessed 2026-11-05.
- Initial Triage and Resuscitation of Small Animal Emergency Patients, Merck Veterinary Manual, accessed 2026-11-05.
- Frequently Asked Questions & Myths, WSAVA Global Nutrition Committee, accessed 2026-11-05.
