Where to Buy Synthroid (Levothyroxine)

By Christine Teal, MD, MPH
Medically Reviewed by Caitlin Rausch, PharmD, BCOP
Last Updated: February 12, 2025

What is Synthroid (Levothyroxine)?

Synthroid (levothyroxine) is a medication that helps people with hypothyroidism, a condition where the thyroid gland does not make enough hormones. This can lead to tiredness, weight gain, and feeling down. The drug works by giving your body the thyroid hormone (T4) it needs to keep your energy, metabolism, and body temperature balanced. Doctors usually start with a small dose and adjust it based on blood tests. Most people, about 80%, start feeling better in just a few weeks. For the best results, take it on an empty stomach, at least 30 minutes before breakfast.

Millions of people take this T4 medication daily because it is the most common treatment for thyroid issues. It comes in 12 different strengths, so your doctor can find the right dose for you. However, things like age, pregnancy, or diet can affect how much you need. If you take calcium or iron too soon after this tablet, it might not work as well. Luckily, over 90% of people keep their thyroid levels stable with proper use. But stopping it suddenly can cause serious tiredness or mood changes. That’s why regular check-ups and blood tests are important to keep you feeling your best.

Where to buy Synthroid (Levothyroxine)?

If you take this tablet for thyroid health, ordering online can save time and hassle. No more pharmacy trips—just place an order from a trusted source and have it delivered straight to your door. Many online pharmacies offer secure payments, verified medications, and fast shipping, ensuring you always have your medication when needed.

In 2025, a national poll showed that over 60% of patients now prefer buying this hypothyroidism treatment online due to lower prices, convenience, and reliable shipping. With increasing demand, many trusted online pharmacies provide auto-refill services, bulk discounts, and same-day shipping to make access even easier.

Medication	Active Ingredient	Dosage Options	Why Buy Online?	Best Place to Buy
Synthroid	Levothyroxine	25 mcg – 200 mcg	Easy refills, lower prices, fast delivery	Canadian Online Pharmacy

Simply place your order online, and have these tablets delivered right to your home—so you never miss a dose.

Is Synthroid available over the counter?

No, Synthroid (levothyroxine) is not available over the counter. It is a prescription-only medication because the thyroid hormone levels must be carefully controlled. Taking the wrong dose can lead to serious health risks, including heart problems, bone loss, and hormone imbalances. Doctors determine the right dose based on TSH blood tests, which help track how well the thyroid is working. In the U.S., Canada, Australia, and most countries, you need a doctor’s prescription to buy this thyroid supplement.

To get a prescription, you need a consultation with a doctor, either in person or through an online telehealth service. Many licensed online pharmacies make the process easier by offering prescription transfers, virtual doctor visits, and home delivery. This ensures you get the right dose without unnecessary delays.

FAQ

What is Synthroid used for?

This metabolic booster replaces missing thyroid hormones in people with hypothyroidism. When the thyroid gland does not produce enough hormones, it can cause fatigue, weight gain, and slow metabolism. This endocrine regulator helps restore energy, metabolism, and body temperature regulation. Doctors adjust the dose based on TSH blood tests to ensure the right balance. Most people start feeling better within a few weeks of treatment.

Doctors prescribe this T4 hormone therapy for several conditions, including:

Hypothyroidism – Treats an underactive thyroid by restoring hormone levels.
Goiter (enlarged thyroid) – Helps shrink thyroid swelling by balancing hormone production.
Thyroid cancer treatment – Prevents cancer regrowth by keeping TSH levels low.
TSH suppression therapy – Lowers thyroid-stimulating hormone (TSH) when needed.
Hashimoto’s thyroiditis – Manages autoimmune thyroid disease that causes hormone imbalances.

Because thyroid function affects the heart, brain, and metabolism, taking the tablets as prescribed is essential for long-term health.

What exactly does it do?

Levothyroxine is a medication that replaces thyroid hormone (T4) in people with hypothyroidism. When the thyroid gland does not make enough hormones, the body slows down. This can cause fatigue, weight gain, and cold sensitivity. The drug helps restore energy, metabolism, and body temperature regulation. Doctors adjust the dose based on TSH blood tests, ensuring the right balance. Most patients, about 80%, start feeling better within weeks of treatment.

This medication also supports heart function, brain activity, and digestion by keeping thyroid hormone levels stable. It is essential for growth, muscle strength, and overall body function. Taking the wrong dose can cause serious health problems, like fast heartbeat, anxiety, or bone loss. That’s why regular blood tests help doctors keep thyroid levels safe and effective. More than 90% of patients maintain stable thyroid levels when following their prescribed treatment.

Why is Synthroid taken at night?

Some people take the tablet at night because it may absorb better on an empty stomach. Food, coffee, and supplements like calcium or iron can block absorption, making the medication less effective. Taking it before bedtime, at least 3–4 hours after eating, helps the body absorb it fully. Studies suggest nighttime dosing may lead to more stable thyroid levels, especially for those with inconsistent morning routines. However, consistency is key—take this thyroid imbalance medication at the same time every day for the best results.

How do I use levothyroxine for best results?

To get the best results from this pill, take it correctly and consistently. Absorption matters, so follow these simple steps to ensure maximum effectiveness.

Tips for taking levothyroxine correctly:

Take it on an empty stomach – At least 30 to 60 minutes before breakfast or 3–4 hours after your last meal.
Use a full glass of water – This helps the pill dissolve properly for better absorption.
Be consistent – Take it at the same time every day, whether in the morning or at bedtime.
Avoid certain supplements – Wait at least 4 hours before taking calcium, iron, or antacids, as they can block absorption.
Check with your doctor – Regular blood tests help adjust your dose for stable thyroid levels.
Store it properly – Keep your pills in a cool, dry place away from heat and moisture.

What are the side effects?

Levothyroxine is safe for most people, but some may experience side effects, especially if the dose is too high or low.

Possible side effects of Synthroid:

Fast or irregular heartbeat – The most common side effect, caused by excess thyroid hormone speeding up the heart rate.
Anxiety or nervousness – Some people feel restless, jittery, or unable to relax.
Unintended weight loss – A dose that is too high may increase metabolism too much.
Insomnia or trouble sleeping – Taking the tablet too late in the day can affect sleep.
Headaches or dizziness – Some experience mild headaches or lightheadedness.
Sweating or heat intolerance – The body may feel too warm, even in normal temperatures.
Temporary hair thinning – Some people notice hair loss when starting or adjusting their dose.

Most side effects fade over time as the body adjusts. If symptoms continue, talk to your doctor about changing your dose.

Do you gain or lose weight on this pill?

Synthroid does not directly cause weight loss or weight gain. It restores thyroid hormone balance, helping metabolism return to normal. People with hypothyroidism often gain weight due to a slow metabolism, and once treated, some may lose 5-10% of body weight, mostly from water retention. However, this tablet is not a weight-loss medication, and many patients notice little to no change in body weight.

If the dose is too high, it may speed up metabolism too much, leading to rapid weight loss, heart palpitations, or anxiety. If the dose is too low, weight gain may continue due to ongoing hormone imbalance. For best results, doctors adjust this energy level stabilizer based on TSH blood tests, ensuring safe and effective treatment. If you experience unexpected weight changes, consult your doctor for a dose adjustment.

Are there any contraindications?

Yes, this pill is not safe for everyone. Some conditions or medications can make it dangerous or less effective. Always check with your doctor before starting.

Who should not take Synthroid?

People with untreated adrenal gland problems – It can worsen hormone imbalances.
Those with overactive thyroid (hyperthyroidism) – Extra thyroid hormone can cause serious heart issues.
Patients with recent heart attack – This metabolism support pill can put extra strain on the heart.
Individuals with severe heart disease – It may increase the risk of irregular heartbeat or high blood pressure.
People allergic to levothyroxine or inactive ingredients – Allergic reactions can be dangerous.

Certain medications, like calcium supplements, iron, and antacids, can block levothyroxine absorption. Taking these within 4 hours can make the drug less effective. Always follow your doctor’s advice for safe use.

What foods should you avoid while taking Synthroid?

Some foods can block levothyroxine absorption or make it less effective. To get the best results, avoid these foods around your dose.

Foods to avoid:

Soy products – Soy milk, tofu, and soybeans can reduce thyroid hormone absorption.
High-fiber foods – Too much fiber slows down medication absorption in the stomach.
Calcium-rich foods – Dairy products like milk, cheese, and yogurt can interfere with the thyroid deficiency remedy if taken too close to your dose.
Iron-rich foods – Red meat, spinach, and fortified cereals can block thyroid hormone absorption.
Cruciferous vegetables – Broccoli, cabbage, and Brussels sprouts may affect thyroid function when eaten in large amounts.
Coffee – Drinking coffee within 30 minutes of taking the tablet can lower its effectiveness.

To avoid problems, take the medication on an empty stomach, at least 30–60 minutes before eating.

Can you drink coffee with this tablet?

No, you should not drink coffee right after taking Synthroid. Coffee can block absorption, making the medication less effective. Studies show that drinking coffee within 30 minutes can lower the drug absorption by up to 36%.

What is the right dosage?

The right dosage of levothyroxine depends on age, weight, thyroid condition, and blood test results. Doctors start with a low dose and adjust based on TSH levels. Taking too much can cause fast heartbeat and anxiety, while too little leads to fatigue and weight gain. Most adults need 1.6 mcg per kg of body weight per day, but this varies.

Below is a general Synthroid dosage guide based on common prescriptions:

Dosage Strength	Who It’s For
25 mcg	Low starting dose, elderly, or those with heart conditions
50 mcg	Mild hypothyroidism or gradual dose increase
75 mcg	Standard dose for moderate thyroid hormone deficiency
100 mcg	Common maintenance dose for adults
125 mcg – 200 mcg	Higher doses for severe hypothyroidism

Only a doctor can determine the right dose. Regular blood tests help adjust it for safe and effective treatment.

Synthroid vs levothyroxine: what is the difference?

These are the same medication, but there is a key difference. Levothyroxine is the generic version, while the other is a brand name. Both contain levothyroxine sodium, which replaces missing thyroid hormone (T4) in people with hypothyroidism. Doctors prescribe both, but some patients absorb Synthroid better due to its consistent formula.

The generic version is usually cheaper, but small variations in ingredients may affect absorption in some people. Studies show the brand-name medicine keeps thyroid levels more stable for some patients. If switching brands, doctors monitor TSH levels to adjust the dose if needed. Always ask your doctor or pharmacist before changing your medication.

Is this drug hard on your heart?

Thyroid dysfunction treatment can affect the heart if the dose is too high, leading to rapid heartbeat, palpitations, or high blood pressure. A study in the Journal of Clinical Endocrinology & Metabolism found that excess thyroid hormone increases the risk of atrial fibrillation, a serious heart rhythm disorder. People with heart disease, high blood pressure, or a history of heart attack should take lower doses and have regular blood tests to avoid complications. If you feel chest pain, shortness of breath, or a racing heart, consult your doctor immediately to adjust your dosage.

Why do you have to drink water while taking this drug?

Levothyroxine must be taken with water because it helps the pill dissolve and absorb properly in the stomach. Swallowing it with other liquids like coffee, juice, or milk can reduce absorption, making the medication less effective. Dry swallowing may cause the pill to stick to the throat, leading to irritation or delayed absorption. For the best results, take the tablet with a full glass of water on an empty stomach, at least 30 minutes before eating.

What are signs of too much Synthroid?

Taking too much T4 medication speeds up your metabolism, causing uncomfortable and serious symptoms. The most common sign is a racing heartbeat. Other symptoms include:

Heart palpitations – Feeling like your heart is pounding or skipping beats.
Anxiety and nervousness – Feeling restless, jittery, or overly alert.
Unexplained weight loss – Losing weight even without diet changes.
Sweating and heat intolerance – Feeling too hot or sweating excessively.
Trouble sleeping – Difficulty falling or staying asleep.

Long-term overdose can cause bone loss and heart problems. If you notice these signs, contact your doctor immediately to adjust your dose.

Can I use levothyroxine when breastfeeding?

Yes, you can safely use levothyroxine while breastfeeding. According to the National Institutes of Health, this medication passes into breast milk in minimal amounts, posing no risk to the infant.

Maintaining proper thyroid hormone levels is essential for both mother and baby, as it supports normal milk production and overall health. The NHS confirms that this drug is a normal part of breast milk, and taking it as a supplement introduces only tiny amounts that are too small to affect your baby.

Therefore, continuing your prescribed treatment during breastfeeding is important for your well-being and your baby’s development.

Is the generic version equally effective?

Yes, the generic version of Synthroid is generally considered as effective as the brand-name medicine. A study in JAMA Network Open found that 75.5% of patients on generic levothyroxine achieved normal thyroid-stimulating hormone (TSH) levels, compared to 76.9% of those on brand-name versions.

However, some individuals may respond differently due to inactive ingredients or absorption variations. If you experience symptoms after switching between generic and brand-name versions, consult your doctor. They can monitor your TSH levels and adjust your dosage if needed.

About the Author

Dr. Christine Teal, a board-certified breast surgeon, is the Director of the Breast Care Center and Chief of Breast Surgery at The George Washington University School of Medicine & Health Sciences. She earned her medical degree from the University of Pennsylvania (AOA) and completed her surgical residency at Weill Cornell and Memorial Sloan Kettering. Her research appears in top medical journals, and she is active in the American College of Surgeons and the American Society of Breast Surgeons. She also serves as the Cancer Liaison Physician for the American College of Surgeons’ Cancer Committee.

Disclaimer: This content is provided for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional before making any decisions regarding your medications, treatment, or overall health. If you experience medical symptoms or have health concerns, seek immediate medical attention.