Hyperthyroidism: how to better medicate and monitor cats in your care

Hyperthyroidism is the most common endocrinopathy diagnosed in cats, and clinicians will be very familiar with diagnosis and treatment. However, managing this condition is not without challenges, and optimising care means finding pragmatic ways to improve treatment compliance and personalise patient monitoring.

Supporting caregivers to medicate their cats

Many hyperthyroid cats are treated with oral antithyroid drugs. However, giving oral medication to cats is not easy. In one study (Taylor, Caney et al, 2022), 52% of owners reported that giving medications at home changed their relationship with their cat, 77% reported the cat tried to bite or scratch them and 72% refused medication in food. Another study reported 39% medication non-compliance (Odom, Riley et al, 2025).

Failure to administer medication for hyperthyroidism will result in ongoing unpleasant clinical signs and loss of body and muscle condition which carries a reduced survival time (Vagney, Desquilbet et al, 2018). Additionally, poorly controlled hyperthyroidism will have impacts on the heart, kidneys and other organs. Therefore, managing hyperthyroidism must include supporting caregivers to administer medication, not just prescribing the correct drugs.

For some caregivers, it is initially easy to give medication as the uncontrolled hyperthyroid cat is polyphagic, but as appetite normalises they may begin to struggle and be tempted to miss doses allowing the total thyroxine (T₄) to creep up again.

Tips for medicating hyperthyroid cats include:

• Discussing which formulation caregivers find easiest to administer (most caregivers choose liquid formulations, but some find tablets easier);
• Advising caregivers on different methods of giving medications (directly into the mouth, on a treat) depending on formulation and data sheet recommendations;
• Providing demonstrations in clinic or links to information such as the International Cat Care website (https://icatcare.org/articles/how-to-give-a-cat-medication) on giving medication or adding information to the clinic webpage;
• If medication can be given in food or a treat, adding to main meals should be avoided as this can deter eating, and caregivers should be advised on using liquid treats or pill putty products (Figure 1) that they may not be aware of, but now come in a wide range of flavours and formulations;
• Putting medication in a size 4 gelatin capsule, which is especially useful if cats are on more than one medication (for example, for comorbidities), so they only need be medicated once;
• Following up with caregivers after 48 hours via their preferred communication route (telephone, text, email) to discuss challenges and alternatives if necessary.

For some cats, orally medicating them has significant impacts on quality of life and alternatives such as transdermal methimazole or radioactive iodine, thyroidectomy or dietary management should be considered.

Monitoring hyperthyroid cats is more than just measuring T₄

Within the same clinic clinicians may have different protocols for monitoring hyperthyroid cats. This can lead to confusion and caregivers failing to arrange appointments, particularly if cats are perceived as doing well.

However, monitoring is important to identify complications such as hypertension, which can develop during treatment for hyperthyroidism, even if not present at diagnosis (Taylor, Sparkes et al, 2017). Monitoring is also important to allow dosage adjustments given that hyperthyroidism is a progressive disease (Peterson, Broome et al, 2016), with escalations in medical management often needed over time to maintain euthyroidism.

Additionally, cats with hyperthyroidism are at an age where they may develop comorbidities, which could be missed without regular assessment. Caregivers can be reluctant to present senior cats to the clinic, worrying that this will cause the cat distress or lead to testing and intervention they would rather avoid. Considering how to make the clinic visit cat friendly, can help improve attendance to follow-up appointments (see https://icatcare.org/cat-friendly-clinic).

Although having a fixed “protocol” for monitoring hyperthyroid patients in the clinic can simplify advice, it may need to be adjusted for the individual cat and caregiver and according to the treatment modality selected. The following can be considered:

• “Auditing” the clinic’s monitoring of cats diagnosed with hyperthyroidism; are any being missed and only seen infrequently to acquire medication without assessment of dosage? Could any that have missed check-ups be invited for a recheck?
• Developing a protocol as a guide (flexed to the individual case). For example, once euthyroid on medication, hyperthyroid cats could be routinely seen via senior cat nurse consultations every 3 months to assess blood pressure, body weight, BCS and MCS, escalating to further testing if the cat has lost weight for example;
• If dosages are adjusted, total T₄ should be reassessed after approximately two to four weeks;
• Cats with concurrent hyperthyroidism and comorbidities such as CKD may need closer monitoring based around clinical signs, weight/BCS/MCS and targeted reassessment of T₄ and creatinine.

Optimising hyperthyroid monitoring: a team approach

• Monitoring hyperthyroid patients should involve both vets and vet nurses, integrating nurse clinic checks of medication compliance, weight/BCS/MCS and blood pressure for example (Figure 2), with alternating vet checks to look at dosage adjustments;
• Minimising stressors for hyperthyroid cats in the clinic by creating a cat friendly environment and improving interactions by using pre-visit gabapentin or pregabalin to facilitate blood sampling;
• Client care teams should be clear on which appointments to offer to hyperthyroid patients, namely when the clinic is quiet to avoid stress in busy waiting rooms, nurse clinic appointments and longer vet consultations if blood sampling will be needed;
• Pricing could be reviewed with regards hyperthyroid cat re-check ‘packages’ including consultation (with blood pressure measurement) and lab testing for example so clear and consistent even if seeing different clinic staff, and more cost-effective than pricing tests individually (deterring cost-limited clients);
• Hyperthyroid cat CPD for the clinic teams to discuss the above protocols and costings can be organised (often supported by pharmaceutical companies).

Importance of body and muscle condition

Successful treatment of hyperthyroidism involves regaining lost weight. However, we are increasingly recognising the importance of muscle condition score as a way of assessing health in senior cats. ‘Frailty’ and loss of muscle can reduce quality of life and is negatively associated with survival (Chandler, 2026; Figure 3) yet may not show on the scales. Assigning hyperthyroid cats a muscle condition score (MCS, see https://www.wsava.org/nutrition-toolkit) at each re check can identify those needing further intervention. Such interventions include taking an accurate nutritional history, improving calorie intake and diet quality (particularly in terms of protein), pharmaceutical interventions and supplementing with fish oils. Future directions may include probiotics and creatine for example.

Conclusion and take-home messages

Even if confident in managing hyperthyroidism, there are always areas we can try and improve to optimise care of these patients. Supporting caregivers, reviewing monitoring and involving the whole clinic team can be rewarding and effective.

References

Chandler M (2026). Sarcopenia, cachexia and frailty in older cats: Mechanisms, assessment and therapeutic considerations, J Feline Med Surg 28(7): 1098612X261426765.

Peterson ME, Broome MR and Rishniw M (2016). Prevalence and degree of thyroid pathology in hyperthyroid cats increases with disease duration: a cross-sectional analysis of 2,096 cats referred for radioiodine therapy, J Feline Med Surg 18(2): 92-103.

Taylor S, Caney S, Bessant C and Gunn-Moore D (2022). Online survey of owners’ experiences of medicating their cats at home, J Feline Med Surg 24(12): 1,283-1,293.

Taylor SS, Sparkes AH, Briscoe K, Carter J, Sala SC, Jepson RE, Reynolds BS and Scansen BA (2017). ISFM Consensus Guidelines on the Diagnosis and Management of Hypertension in Cats, J Feline Med Surg 19(3): 288-303.

Vagney M, Desquilbet L, Reyes-Gomez E, Delisle F, Devauchelle P, Rodriguez-Pineiro MI, Rosenberg D and Fornel-Thibaud P de (2018). Survival times for cats with hyperthyroidism treated with a 3.35 mCi iodine-131 dose: a retrospective study of 96 cases, J Feline Med Surg 20(6): 528–534.