Experienced and professional animal trainer provide their insights in answering this question :
A. Your dog will be fine. Levothyroxine is not dangerous at this dose.

How to Identify Common Pet Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced pet care professionals :

Clinical signs of thyroid hormone toxicosis in dogs and cats include hyperactivity, lethargy, tachycardia, tachypnea, dyspnea, abnormal pupillary light reflexes, vomiting, and diarrhea.
INDICATION: For replacement therapy for diminished thyroid function in dogs. DOSAGE AND ADMINISTRATION: The initial total daily dose is 0.1 mg/10 pounds (0.01 mg/lb; 0.022 mg/kg) body weight as a single dose every 24 hours or as a divided dose every 12 hours.
Massive amounts of levothyroxine may be ingested intentionally or accidentally. The most common intentional reasons include weight loss and suicidal ideation among others. A potentially toxic dose includes acute ingestion of more than 5 mg of levothyroxine or 0.75 mg of triiodothyronine [3].
Side Effects of Thyroxine Use

If given at too high of a dose, your dog may experience thyrotoxicosis. Signs of this may include increased heart rate, appetite, drinking, urination, excitability, panting, and nervousness.

The second is the high dosing of levothyroxine in dogs when comparing it to human dosing. This difference has also resulted in dispensing errors. The half-life of levothyroxine in canines is only 10 – 16 hours, compared to ~7 days in humans.
The half-life of levothyroxine in dogs is 10 to 16 hours.
Humans often require less levothyroxine needed to treat hypothyroidism. Dogs absorb and metabolize levothyroxine differently than humans. As a result, they may need higher doses than seen in humans.
Levothyroxine is absorbed in the small intestine and is 70%-80% bioavailable in the euthyroid individual. Peak absorption is achieved at approximately 2 hours after oral ingestion but can be delayed to 3-4 hours if it is ingested simultaneously with interfering medications, supplements, or some foods/drinks.
The average full replacement dose of levothyroxine sodium is approximately 1.7 mcg/kg/day (e.g., 100-125 mcg/day for a 70 kg adult). Older patients may require less than 1 mcg/kg/day. Levothyroxine sodium doses greater than 200 mcg/day are seldom required.
Levothyroxine may cause serious or life-threatening problems when given in large doses, especially when taken with amphetamines such as amphetamine (Adzenys, Dyanavel XR, Evekeo), dextroamphetamine (Dexedrine), and methamphetamine (Desoxyn).
The thyroid hormone thyroxine increases both basal metabolic rate and urinary water loss in mammals. Increases in basal metabolism and urinary water loss are likely to be detrimental to D. merriami, therefore the regulation of this hormone may be important.
What does the thyroid do? The thyroid is a gland located in your dog`s neck which produces essential hormones that work to regulate your dog`s body temperature and metabolism.
Synthroid is brand name levothyroxine sodium; other brand name versions of levothyroxine include Levothroid, Unithroid, Tirosint, and Levoxyl. It contains the same active ingredients and is used for the same purposes, namely to treat hypothyroidism or low thyroid hormone levels.
Levothyroxine is a synthetic (man-made) version of thyroxine, or T4, the main hormone that is made and released by your thyroid gland. 1 Levothyroxine is prescribed for people with an underactive thyroid, a condition known as hypothyroidism. Most medications are available in brand-name and generic preparations.
The absorption of levothyroxine in the gut is decreased when taking the hormone at the same time as calcium, iron and some foods and other drugs. Because of this, patients are usually instructed to take levothyroxine on an empty stomach 30-60 minutes before food intake to avoid erratic absorption of the hormone.
Because you absorb levothyroxine in your small intestine, dosing instructions recommend taking the tablets on an empty stomach. You should then wait an hour before eating to allow for the pills to dissolve and start being absorbed.
When you start levothyroxine you won`t feel better the next day. You may not feel better in two weeks. But symptoms should start disappearing within a month. After six weeks of treatment, you should be almost completely free of symptoms, assuming you`re at the right medication level.
Levothyroxine is used to treat an underactive thyroid (hypothyroidism). It replaces or provides more thyroid hormone, which is normally produced by the thyroid gland. Low thyroid hormone levels can occur naturally or when the thyroid gland is injured by radiation/medications or removed by surgery.
Your dosage will be based on several factors, including your age, weight, thyroid hormone levels, other conditions you have, and other medications you take. The typical dosage is 1.6 mcg/kg/day. Dosages are usually less than 200 mcg/day.
Taking Too Much Thyroid Hormone and Thinking It`s Harmless

But taking an excessive amount could have side effects — it can make you feel tired, affect your sleep and concentration, lead to bone loss, or cause irregular heartbeats, according to the Cleveland Clinic.

Medication for hypothyroid dogs

Treatment for hypothyroidism involves boosting the low hormone with a synthetic (manufactured) hormone called levothyroxine. Most dogs receive levothyroxine twice daily, but some dogs do well on once-daily treatment.

Official answer. Most foods are considered fine to eat for breakfast as long as they are eaten 30 to 60 minutes after taking levothyroxine. Levothyroxine should be taken once a day on an empty stomach in the morning. Taking the medication on an empty stomach is recommended because it increases absorption of the drug.
The common clinical signs following thyroxine overdose can either be limited to tachycardia, agitation, nervousness, insomnia, anxiety, tremor [2], or severe features, though less likely, like thyroid storm involving cardiac, neurological, respiratory and thermoregulatory center [3].
This can cause your T4 hormone levels to drop or fluctuate. To avoid this, levothyroxine should be taken on an empty stomach, and you should wait an hour before eating anything or drinking a caffeinated beverage.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Q. My 75 lb GSD may have swallowed my mother’s 75 mg levothyroxine… Will he be ok?
ANSWER : A. Your dog will be fine. Levothyroxine is not dangerous at this dose.

Q. Male neutered cat [1 1/2 years old] has just started trying to spray everywhere around the house. Nothing is coming out. No recent changes.
ANSWER : A. Changes in urinary habits can be caused by a number of things, especially in neutered male cats. Attempting to urinate or have accidents in places other than the litter box can often be a sign of a urinary tract infection, or crystals and debris in the bladder causing problems. Pets may need to go more frequently, may dribble or urinate in small amounts more often, may have accidents or may have blood-tinged or cloudy urine.Infections are usually treated with medications and changes to the diet, however in some cases of large stones or crystals surgery may be needed.

Male cats can also experience urinary blockage. This is due to a unique anatomical part or the urethra that forms a U-shape before exiting the body in male cats. If a cat has crystals or other debris in the urine, it can block at this point preventing urine from being able to exit. Cats may attempt to urinate without producing anything, may become very vocal (indicating pain) or may have a hunched back, full abdomen or pain in the abdomen (protecting the very full bladder). Urinary blockage IS a medical emergency so if suspected, your vet or local emergency clinic should be contacted immediately. Treatment usually involves a hospital stay and catheterization of the bladder to remove the blockage and allow urine to drain followed by medications and a change in diet to prevent further problems.

It is best to try and collect a sample of urine and make an appointment for your cat if he has had a change in urinary habits. If you do suspect a blockage, then contact your vet ASAP is best.

Q. My 20 month Cavalier doesn’t eat unless I let him eat from my finger, then he eats. Sometimes he will only eat once a day and leave his food.
ANSWER : A. It is possible that your dog is just not satisfied with his current food, or may be a picky eater. There are several things you can try to encourage your dog to eat.

The first step is to remove any additional treats or people food that may be more enticing to your dog than his own meal. If you feel you must give him some form of treat, be sure to place them directly in his food bowl and mixed with his regular diet. This allows him to get some snacks while also “forcing” him to try out his current meal to get the reward.

Enticing your dog to try his food by adding a pet-safe gravy or even a few treats of plain boiled chicken mixed in can help. Be sure to mix the foods thoroughly so he must explore his own food before getting the treat.

Some small breed dogs may also have a hard time with certain bowls and their collars. If there is a metal name tag on the collar and a metal bowl, the clinking sound can sometimes scare off dogs and make them not want to eat from their bowl. Using a bowl of a different material, or removing the collar prior to a meal may help with this issue.

Your dog may also just not be into his current food and may like another variety better. You can try a new variety by gradually switching over a period of 7-9 days, slowly adding in more new food and removing old until it is switched. This change may encourage him to try out meals again, and the slow changeover will allow his body to adjust to the new diet without digestive upset.

Q. My dog has a hard time walking on his front legs. I was told he has nerve damage and he was walking on three legs now it seems to be both front legs
ANSWER : A. Problems with walking in the front legs can be caused by a large number of things. Arthritis in older dogs can cause joint pain and stiffness which may make walking hard. Nerve or muscular damage may also cause problems.

With nerve or muscle damage there is often a loss of muscle tone in the affected limbs. Limbs may look skinnier than unaffected ones, and may lose overall muscle mass. In some cases, treatment for pain or soreness may help improve symptoms some. Depending on the severity of the damage, some dogs may recover while others have permanent damage.

It may also be that if your dog was putting all his weight on one front leg to help the other, that the good front leg is now stiff and sore. Restricting exercise, giving a supplement to help joints and bones and following your veterinarian’s recommendations for care can all help your dog to feel a little better.

Q. Husband shamed dog for having an accident inside, and now she won’t poop when he takes her out. Can we fix this? He realizes he erred
ANSWER : A. Good on your husband for realizing that scolding is not the way to potty train! Hopefully these tips can help both him and your pup get back on the right track and make pottying outside successful.

If your dog is still a puppy, that is good news as you may be able to more easily time your potty outings with your dog’s schedule. Even if your dog is older, this schedule may help. Dogs generally have to go potty about 15 minutes after eating, drinking, waking up or playing. Knowing this, get your husband to start taking out your puppy at these key times, so puppy gets used to going out with him, and the urge to potty may be higher than any fear to go. If the potty is successful, have your husband reward the dog with a favorite treat! For bowel movements, dogs may take a little more time, and you may have to stand outside for a while (sometimes even 10 minutes) to give your dog a chance to go. If she doesn’t go, take her back inside and play some, then try again in about 15 minutes. Again, a success equals a treat which most dogs will like right away!

For any indoor potty accidents that occurred, an enzymatic cleaner is great for cleaning up urine and stool. Not only does it remove the stain and smell, but it breaks down the enzymes in the urine and stool your dog can smell, which may deter her from going potty there again.

Q. My GSD has eye and nasal infection both parts are always bleed.im very worried about him please suggest me what should I do
ANSWER : A. If your GSD is being treated for eye and nasal infections currently and you are seeing bleeding, it is best to contact the vet that prescribed any medication and treated your dog initially. It is possible that the medications are causing a reaction, the illness is worsening, or there may be a foreign body or other object stuck in the nasal cavity that is causing bleeding (tumors, seeds and other objects may all cause bleeding along with nasal discharge and watering of the eyes). If you CAN see a foreign body, do NOT attempt to remove it yourself as this may cause more damage to the nasal cavity or cause it to become lodged further back. Your vet should be able to sedate your dog and take a look for signs of a foreign body, or may also prescribe additional medications to help relieve symptoms and treat any underlying infection.

Q. My Greyhound starts to chatter his teeth and shake. It’s not cold inside and it doesn’t last long. He might even go outside quite a bit. Suggestions?
ANSWER : A. Even if things seem room-temperature to you, greyhounds have very little hair and may still get cold. Adding in a sweater or doggie coat may help him to feel a little more comfortable. You may also want to add a blanket to his bedding to snuggle under as well. Teeth chattering may also indicate nervousness or stress, and if you’ve had recent changes to your home (such as new people or pets) this may be a cause as well. Providing a place for him to rest away from all the commotion may help.

If you are seeing any other signs of illness in addition to the teeth chattering such as drooling, vomiting, diarrhea or lethargy, then alerting your vet is best.

Q. Early in the morning she goes licking everything, the bed, pillow and all. Tried giving her water but refuses to drink. Any advice?
ANSWER : A. Licking can sometimes be medical or behaviorally caused. As with any sudden new behavior in your pet, it is a good idea to schedule a wellness exam with your vet to make sure there are not any health issues causing it.

Behaviorally, licking can be an anxiety-related behavior, and may become habitual to your pet. If something stressful is happening in the morning such as people going to work, kids waking up and being noisy, or new routines, it may have caused a sort of “ritual behavior” from your pet in the form of licking. Identifying the stressor may help to break the habit.

Giving your pet a calm place to relax in the morning may help, as may providing a pheromone diffuser to help during any stressful transitions. These release a calming pheromone that can help reduce stress-related behaviors. Also offering something GOOD to lick such as a Kong filled with peanut butter, or an ice cube to move around the house may keep her occupied and licking that instead of your furniture.