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Leventa Oral Solution for Dogs

  • 30ml Bottle £16.99

Leventa is used to treat an under active thyroid gland in dogs (hypothyroidism). The typical signs of this condition are weight gain, lethargy, poor, patchy coat, skin problems and reduced breeding performance. The condition is characterised by low natural blood levels of the hormone thyroxine, produced in the thyroid gland. However many cases of hypothyroidism in dogs are difficult to diagnose accurately, because of the wide overlap in blood test results between normal and affected dogs. Vets can perform additional blood tests to diagnose the condition. Once therapy with Leventa has been started, a gradual resolution of clinical signs is expected.


Clear, slight reddish coloured solution.

Each ml contains:

Active substance: Levothyroxine sodium (as multihydrate) 1 mg (equivalent to 0.97 ml levothyroxine).

Excipient: Ethanol 96% 15 ml


Treatment of hypothyroidism in dogs.

Dosage and administration

For oral use only. In thyroid hormone replacement therapy with L-thyroxine, the dose rate and regime have to be tailored individually to each dog. A starting dose rate of 20 µg L-thyroxine sodium/kg once daily is recommended; this corresponds to 0.2 ml of the product per 10 kg bodyweight. At re-examination four weeks later, dose adjustment should be performed based on the clinical response to treatment and thyroid hormone concentration evaluated 4-6 hours after administration of the product. Further assessment of hormonal responses and dose adjustment may be repeated at 4 week intervals if required. A maintenance dose rate between 10 and 40 µg/kg body weight once daily is generally sufficient to control the clinical signs of hypothyroidism and to restore thyroid hormone concentrations to within the reference range. Depending on the dose rate determined as suitable for the dog and on its body weight, the volume (in ml) of the product to be administered once daily can be estimated using the Dosing Guide table:

Table 1 - Dosing Guide for Leventa

Leventa table 100

Once a suitable dose rate and regime have been established, it is recommended to recheck every 6 months that thyroid hormone concentrations are appropriate. The improvement in clinical signs occurs differentially following the onset of treatment with L-thyroxine: whilst metabolic signs improve within two weeks after the onset of treatment, dermatological signs may require 6 weeks or more of treatment before improvement is seen. The product should be administered at the same time every day. The absorption of L-thyroxine is influenced by food. In order to achieve consistent absorption of L-thyroxine, it is recommended to administer L-thyroxine 2-3 hours prior to feeding, which will maximise the degree of absorption and minimize variation in absorption. If L-thyroxine is administered less than 2 hours before feeding, at or after feeding, the feed given (type and amount) should be standardised.

Instruction for use of the oral syringe: Open the bottle. Attach the dosing syringe to the bottle by gently pushing the end of the syringe onto the insert in the bottle. Turn the bottle/syringe upside down and draw the solution into the syringe by pulling the plunger out. The edge of the ring on the end of the plunger should align with the expected volume or body weight in kilograms. Turn the bottle/syringe the right way up and remove the syringe from the insert. After administration, clean the syringe with clean water and allow to dry naturally.

See diagram.

Leventa oral syringe diagram2

Contra-indications, warnings, etc

Do not use in dogs with hyperthyroidism or uncorrected adrenal insufficiency (hypoadrenocorticism). Do not use in case of hypersensitivity to levothyroxine sodium or to any of the excipients. The product should be used with caution in dogs with cardiac disease, diabetes mellitus or treated adrenal insufficiency (hypoadrenocorticism). For these dogs, gradual introduction of levothyroxine therapy, starting with 25% of the normal dose and increasing by 25% increments every two weeks until optimal stabilisation is achieved is recommended. The clinical diagnosis of hypothyroidism should be confirmed by laboratory tests. Adverse reactions associated with L-thyroxine sodium treatment are primarily those of hyperthyroidism, due to therapeutic overdose. They include weight loss, hyperactivity, tachycardia, polydipsia, polyuria, polyphagia, vomiting and diarrhoea. Transient, self-resolving skin reactions such as mild to moderate scale formation may occur.

Use in pregnancy

The safety of use in pregnant bitches has not been evaluated. However, thyroxine is essential for normal foetal development. Hypothyroidism during pregnancy may be associated with impaired cognitive development and increased foetal mortality. During pregnancy, maternal thyroid hormone requirements may increase. Pregnant bitches receiving treatment should therefore be monitored on a regular basis from conception until several weeks after delivery, as dose requirements may change during pregnancy and lactation.

Use in lactating bitches or animals intended for future breeding has not been evaluated.

Drug interactions

L-thyroxine absorption may be impaired by the concurrent administration of antacids, e.g. aluminium or magnesium salts or calcium carbonate, or ferrous sulphate and sucralfate. Therefore, concomitant administration of Leventa with the above mentioned compounds should be avoided. At least 2 hours should elapse between administration of Leventa and such products. The therapeutic response to Leventa may be altered by any compound that influences thyroid hormone metabolism and disposition (e.g. drugs displacing protein-binding site, modifying serum thyroxine-binding globulin concentration, or altering hepatic degradation of thyroxine or peripheral conversion of thyroxine to triiodothyronine). Thus, in case of concomitant administration of Leventa with a compound exhibiting one of these properties, it is recommended to recheck that thyroid hormone concentrations are appropriate and to adjust the dose of Leventa accordingly if needed.

Conversely, L-thyroxine supplementation may affect the pharmacokinetics and activity of concurrent therapies. In diabetic dogs treated with insulin, L-thyroxine supplementation may alter insulin requirements. In dogs with cardiac insufficiency, therapeutic response to cardiac glycosides may be decreased by L-thyroxine supplementation. Therefore, if treated with any of these compounds, dogs should be monitored carefully during initiation of treatment with Leventa.


Clinical signs of overdose with L-thyroxine are identical to those of hyperthyroidism and include body weight loss, hyperactivity, tachycardia, polydipsia, polyuria, polyphagia and diarrhoea. These signs are generally mild and fully reversible. Overdose may be accompanied by reversible changes in blood biochemistry, e.g. elevated glucose, inorganic phosphorus and albumin:globulin ratio, and reduced total protein and cholesterol. In a tolerance study, healthy dogs treated with the product at 40 µg/kg body weight once daily during 91 consecutive days did not present any relevant clinical sign. At dose rates of 120 and 200 µg/kg body weight, dogs did not exhibit signs other than those of hyperthyroidism, mainly body weight loss. These signs were mild and reversible, with recovery occurring within 5 weeks after cessation of treatment. Standard measures should be taken to remove non-absorbed drug from the gastro-intestinal tract. If chronic overdosage is suspected, the dose should be re-evaluated.

Operator warnings

In the case of accidental ingestion, seek medical advice immediately and show the package leaflet or the label to the physician. Note: this product contains a high concentration of L-thyroxine sodium and may present a risk to humans if ingested.

Wash hands after use.

In case of eye contact, flush immediately with water.

Withdrawal periods

Not applicable.

For animal treatment only. Keep out of the reach and sight of children.

Pharmaceutical precautions

Store in a refrigerator (+2°C to +8°C). Store in the original container. Once opened use the product within 6 months.

Legal category


Packaging Quantities

30 ml amber glass bottle with a transparent LDPE insert and with a white HDPE child-resistant cap with tamper-proof closure in a printed carton.

A 1 ml oral syringe graduated in 0.05 ml increments is supplied with the product.

Pack sizes: 1 x 30 ml, 6 x 30 ml and 12 x 30 ml. Not all pack sizes may be marketed.

Further information


Marketing authorisation number

Vm 01708/4527.

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