Which is Better, Synthroid or Armour Thyroid Medication

Which is better, Synthroid or Armour Thyroid Medication

Which is the best thyroid medication for hypothyroidism?

I am asked this question all the time and my answer is always the same, “It’s individual.”

While some do great on T4-only levothyroxine medications like Synthroid, commonly prescribed by mainstream doctors, many of us continue to feel horrible on these drugs. My life changed when I found an open-minded thyroid doctor who listened, really listened, to me and my symptoms. Careful trial and error with thyroid medication brands and dosages and I found my “sweet spot”. With stress, age, and the onset of perimenopause, my “sweet spot” has changed over time, and thankfully each time we find my new “fabulous”.

I take a combination of Nature-throid (a brand of natural desiccated thyroid) and a compound time-release T3 (created by a compounding pharmacy). Oh boy does dosage ever make a difference for me. I feel terrible when my Free T3 is low or even middle of the range. I feel fantastic when its at the top quarter of the normal range. Finding what is right for my body has been life-changing. I feel better today at 46 years old than I felt at 30…yes really. I hope the same for you.

Written by Suzy Cohen, RPh

When you’re taking medicine, eating properly and still suffering, you might begin to wonder if your thyroid medication is the problem. It’s a valid thought process. Medication should help you feel better.

I am often asked, which is the best medication to take, but there is not a simple answer to that because we are unique individuals. Because I have been a Registered Pharmacist for 26 years, and I’m a thyroid expert, I’m also asked “What’s the difference between Synthroid and Armour Thyroid?”

While both are used to replace thyroid hormone, the differences are pretty substantial. I’d like to share those now so you can make more informed decisions about what you take. I think this could really help you figure out how to make the most of your medicine, lab work, and dietary supplements.

Synthroid is a pure T4 drug and Armour Thyroid is an NDT drug (Natural Desiccated Thyroid) drug. The very names of these medications cause confusion.

From now on, whenever you read “T4” you can think of that as the same exact hormone that is secreted from your thyroid gland. Synthroid is just a T4 hormone that is a medication. It requires prescription, and your own thyroid gland makes this naturally. T4 is not active in the body, it has to be processed and turned into T3 which does all the good stuff.

Armour Thyroid is an NDT drug, which stands for Natural Desiccated Thyroid. It is a glandular medication that comes from animal sources. It combines T4 and T3 so sometimes people feel better on this because they are actually taking T3 hormone.

Pure T4 Drugs by Other Names
Synthroid is a very popular medication that is pure T4, but there are other names this medication goes by. For example, Levothyroxine, Levothroid, Unithroid, and Tirosint.

NDT Drugs by Other Names
Armour Thyroid is an NDT medication that combines T4 and T3. There are other brand names that work in a similar way that are porcine-derived as well. These include Nature Throid (which is gluten free), WP Thyroid, and Erfa Thyroid (from Canada).

There is also synthetic T3 (like Cytomel) and Compounded T4/T3 (created by specialty compounding pharmacies).

This is how Synthroid and Armour Thyroid differ
(They are different in 8 ways)

1. Synthroid is bio-identical to human T4 (thyroxine) hormone. Armour is derived from pigs, then purified, so it is not bio-identical to human thyroid hormone.

2. Synthroid is not derived from animals, it’s made in a laboratory. Armour is animal-derived and purified in a laboratory. More specifically, Armour is known as an NDT medication, short for Natural Desiccated Thyroid, and it is porcine-derived from the thyroid glands of pigs.

3. Synthroid contains T4 (thyroxine) only, whereas Armour contains both T4 and T3 (tri-iodothyronine). T3 is more biologically active than T4.

4. Synthroid’s actions may take a few hours, whereas Armour Thyroid will begin to work within an hour. What you should feel is more energy, some warmth if you are frequently cold, and more mental clarity. Your heart rate may increase a bit, but not to an uncomfortable level.

5. While possible, it’s unusual that Synthroid triggers an autoimmune response in a person with Hashimoto’s thyroiditis. Sometimes for people with Hashimoto’s their bodies ‘see’ the porcine-derived thyroid hormone and launch an attack against that because it is glandular. While rare, this explains why some of you with Hashimoto’s might feel a little better on Synthroid or a synthetic combo of T4 and T3 (such as taking a combination of Synthroid and Cytomel). It’s very individual of course. This is not a blanket statement, merely a consideration if you have Hashimoto’s and you feel worse on NDT drugs.

6. The inactive ingredients differ. Our bodies are all different in terms of sensitivities to these various ingredients which explains why some people react poorly to certain brands of thyroid medication.

Synthroid- Inactive ingredients include acacia, confectioner’s sugar (contains corn starch), lactose monohydrate, magnesium stearate, povidone, and talc.

Armour Thyroid- The inactive ingredients are calcium stearate, dextrose, microcrystalline cellulose, sodium starch glycolate and opadry white (colorant).

7. Synthroid may take approximately 4 weeks to cause any real alterations in your labwork, whereas Armour (and other NDT drugs) may impact your labwork within 2 weeks. Labs are usually drawn every month or two until symptoms have stabilized so expect to do a little trial and error.

8. Synthroid is measured in milligrams, Armour is measured as “grains” so if you switch between these medications, it’s difficult to figure out what dose you need. Later on in this article, you will find a handy list I created for you titled, Thyroid Hormone Dosage Equivalents. See below.

This is what Synthroid and Armour Thyroid have in common
(They are similar in 8 ways)

1. Neither one corrects auto-immune dysfunction they just help to restore thyroid hormone levels. This means that if you have an over-reactive immune system, it will continue to destroy your thyroid gland tissue despite the medicine you take. This is why there is more to Hashimoto’s than taking thyroid medication. Hashimoto’s is the number one cause of hypothyroidism, yet many hypothyroid patients have no idea because thyroid antibodies are not often tested in mainstream medicine.

2. They both have the potential to form Reverse T3 in your body. Both Synthroid and Armour Thyroid have the ability to create the hibernation hormone rT3 after you take them. If you have Reverse T3 levels that are high, the way to help yourself is not by changing medication, but rather by forcing the conversion of your medications in an active direction. Since T4 (thyroxine) can be metabolised in two directions, forming an active hormone, and an INactive hormone (rT3), it’s best to test yourself for levels of both free T3 and reverse T3.

Thyroid Hormone Conversion

3. Both medications are best taken in the morning because they produce energy, so if you take them at night, it could cause insomnia. (Although some people do great taking their medication before bed. We’re all individual. If you’re taking a T3 medication like natural desiccated thyroid, also speak to your doctor about whether splitting your dose so that you take half of your dose two times a day, for example half first thing in the morning and the other half in the early afternoon, instead of all at once might be more effective for you.) Both medications should be taken on an empty stomach.

4. For all practical purposes, the side effect profile is similar. Thyroid medications are stimulants so regardless of their brand name, they do the same thing. They turn on your fat-burning switch and they improve energy levels.

5. They both require a valid prescription in the United States.

6. Taking these medications will necessitate the need for the same exact lab tests.

7. Neither medication will prevent the development of thyroid cancer, one of the fastest growing cancers in the world. These medications are not anti-cancer, they are hormone replacement drugs.

8. Drinking coffee within 30 minutes of these drugs might significantly reduce their effectiveness. Wait at least one hour before eating and at least three to four hours before taking any vitamin with iron including multivitamins and prenatal vitamin supplements with iron.

You have to convert medication for it to work

Synthroid doesn’t work until your body activates it. It is a T4 drug and your cells require T3 to effectively wake up, burn fat, and feel happy. So you have to convert the T4 into T3 and some medications get in the way of that. See below. Remember this point, if you’re low in T3 and you take a T4 drug, it’s like putting wiper fluid in your gas tank. It does you no good.

Medications interfere with conversion of T4 to T3

Some drugs practically put a STOP sign in front of T4 and prevent its conversion to T3 which is biologically active. Among the most common offenders:

Beta blockers


Oral contraceptives (pills, patches, shots, etc)

Hormone Replacement Therapy



Corticosteroids (Prednisone, Hydrocortisone, etc)


If you are taking any of these medication, you may feel better on an NDT drug because a T4 drug will not easily convert to T3.

Feeling good requires vitamins and minerals

Feeling good requires conversion of Synthroid (or any T4 drug) to its biologically active metabolite T3.

In order for you to convert a T4 drug into a biologically active form, you need several vitamins and cofactors. So if you’re taking Synthroid, for example, then it might be a good idea to have the following nutrients on board (to help drive the conversion into a biologically active form). You don’t have to necessarily supplement (ask your doctor to test your levels), you could try to eat a clean, healthy diet.



Vitamin A





Vitamin B6

Vitamin D


Cortisol levels

Having imbalances or deficiencies of these nutrients can prevent your ability to get well. Many people don’t realize that acid-reducing medications, estrogen-containing hormones, benzodiazepines, opiate analgesics, blood pressure pills, diuretics, statins, even coffee and wine could deplete levels of these nutrients, thus getting in the way of you feeling good. It’s what I call the Drug Mugger effect, based on the title of my book Drug Muggers: Which Medications Are Robbing Your Body of Essential Nutrients–and Natural Ways to Restore Them. If you take any of those medications, you might need to supplement with the above nutrients if you take a T4 drug. It’s a conversation to have with your physician because you might feel better on a pure T3 drug, a combination of T4 and T3, or NDT options.

Iron deficiency, for example, leads to very poor T4 to T3 conversion, so you become clinically hypothyroid which slows metabolism. The net result is weight gain.You may think you’re tired because you have low iron, and less oxygen is carried around your body, but you’re probably not terribly anemic, it’s more likely that you are “thyroid sick” due to poor T3 activity. Take a look at all the drug muggers of iron on page 89 of my book Thyroid Healthy.

Drug muggers of iron

So what is the right dose of medication?

Your dosage is based upon several very important factors, it’s not a one-size-fits-all. Initially dose determination should be based upon:

1. Your age
2. Other health conditions
3. History of heart problems
4. Other medications you take which might interact
5. Severity of symptoms that you’re facing
6. Length of time you have been chronically ill
7. Laboratory tests that evaluate T3, T4, rT3, TSH, and antibody levels to TPO and TG
8. Morning basal body temperature

Have you checked your morning basal body temperature?

Check Morning Basal Body Temperature for Thyroid

Here is page 52. Get a copy of your lab results and check that you’ve had all these tests done and that your levels are optimal not just normal.

Suzy Cohen's book "Thyroid Healthy"

Most of you will begin a medication dose and based upon how you feel, you will either increase or decrease your dose. Hopefully you have a doctor who listens to you and your symptoms. If you develop palpitations, sweating and insomnia, you are taking too much. If you still feel cold, tired and remain overweight, you might need a higher dose, or a second dose during the day. Dosage changes should always be discussed with your physician. There will be times when you will go through life and have to increase your dosage. It’s hard to know exactly, but here’s a good rule of thumb.

When to increase dosage

Based upon labs, if your free T3 is low, you might need Cytomel or Compounded T3 or NDT.

Big life changes, maybe you’ve moved or lost your job, maybe you had a baby.

During a crisis, you may need more adrenal support, you cannot have thyroid problems all by itself. The thyroid and adrenal work together.

After surgery, it’s very common to need more medication or supplemental support.

Keep in mind we are all unique and we have various sensitivities. Please don’t ever double up on your medication, that is dangerous. If you forget a dose, do not double up, just take it the next day when it is due.

Thyroid hormone dosage equivalents

NDT porcine-derived drugs like Armour Thyroid are measured in “grains” not milligrams.

T4 drugs like Synthroid are measured in milligrams.

It’s sometimes difficult to figure out what you are taking, and how your dose has changed if the doctor alters your medication. The following chart might come in handy.

Thyroid hormone dosage equivalents

What if you’re doing everything right, and you still feel bad?

If you are taking thyroid medication, and still not feeling well, one big secret is that your adrenal glands are still not nourished. Your recovery will go faster if you think of your adrenal glands whenever you think of your thyroid gland. These two organs are connected through the HPA axis, the hypothalamic pituitary adrenal axis. There is a connection that most physicians dismiss, and if you only treat your thyroid gland, your recovery will be slower, or incomplete. Ashwagandha is a wonderful adaptogenic herb that supports both thyroid and adrenal health. It also induces relaxation, so if taken at night, it could help with relaxation.

About Suzy Cohen, RPh

Suzy Cohen has been a licensed pharmacist for 25 years and is a functional medicine practitioner for the last 15. You may have seen Suzy on The Dr. OZ Show (6 different appearances), The View, The Doctors, Good Morning America Health, and hundreds of morning shows. Her supplement line called Script Essentials includes a supplement specially designed for thyroid disease called Thyroid Script.

READ NEXT: 10 Things That Stopped My Thyroid Hair Loss

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About Dana Trentini

Dana Trentini founded Hypothyroid Mom October 2012 in memory of the unborn baby she lost to hypothyroidism. This is for informational purposes only and should not be considered a substitute for consulting your physician regarding medical advice pertaining to your health. Hypothyroid Mom includes affiliate links including the Amazon Services LLC Associates Program.


  1. jean rogers says

    Learned a lot yet still confused
    After all I read I believe I should start off with NDT. Sounds like money had gotten in the way as usual & people come in last. I was taking levothyroxine for a hypothyroid. Every morn hr before eating. Followed this plan for 3 yrs didn’t feel different but Dr wanted me on it. After my stroke I gave it up. It was useless. But I am still sluggishly tired but I think I’ve found an answer. What books are the best for me to buy that I could study for my personal answer? TY

  2. Joanne McIntyre says

    I am 72 years of age. Had total thyroidectomy 38 years ago due to hashimoto’s disease. Had been on Eltroxin for most of the time. Now product ingredients had been changed and only Levothyroxine sodium is available in South Africa. I do have constant fatigue and irritability. Also due to hashimoto’s I developed carotid artery rteiosclarosis.

  3. Thank you for this information. I very much appreciate it.

  4. I was given radioactive iodine to treat Graves disease when I was 24 then on going with synthetic T4 until I found Dr to prescribe me with Tarithyroid (Amour) when I was 38 which I had been taking successfully until my recent bloods showing normal T4 high T3. My GP relocated and have since gone back to an old GP that is not so open minded. I am now 50 and he wants me to go back on T4 synthetic thyroid. Struggling to know what to do, any information would be truly grateful. I have been taking Lugols Iodine, B12 and have low iron. kind regards

  5. I am 57 and my energy level is super high. I have never felt better in my life. I have suffered from depression and anxiety throughout my lifetime, but right now I am the happiest I have been. I am very active (tennis, running, kickboxing, yoga) and eat a healthy low-carb diet. I take no medications. Now, my gyn (who is very good) tested my blood for TSH and it has gone from 4 in recent years to 9. She insists I need to take medication and I took Synthroid for three mornings and on the third day was extremely anxious and depressed. Very out of character. I stopped taking it. I had asked to be tested for T3 and T4 and my doctor’s nurse said that is tested only after a month on Synthroid. I don’t know what to do, because I feel so great and don’t want to feel horrible.

  6. My granddaughter is 13 years old she has a Hyperactive thyroid she has been on Levothyroxine for 2 years. She has tired to be a norm kid and stay up with friends struggling with being tired and having trouble getting up for school. She has now faced that she may never be normal she goes to bed by 6 or 7 so she can make it to school have ask doctors to switch medication but won’t one night she slept for 19 hours what do you do were crying out for up and nobody cares.

    • colby zethraeus says

      I think you mean hypothyroidism which is under active thyroid. They only prescribe levothyroxine to under active thyroid, I believe someone correct me if I am wrong. I have hypothyroidism and I take levothyroxine. If I don’t take enough of the medication I am tired and lose hair. I would try upping her dosage. Even though my levels were in the normal range I was still tired and losing hair. I was only taking half or a 25 mcg tablet. For me once I upped my dosage to a whole tablet energy levels came back and I quit losing hair. Hope this helps also have her checked to see I her T3 levels as Levothyroxine only supplies T4 your body has to convert T4 into T3 and she might be having issues with the conversion. I am learning more about thyroid issues all the time.

    • Synthroid is the worst thyroid replacement, as far as I’m concerned. If you’re unable to convert the T4 to T3, then it’s useless, or worse, stored in your body somewhere it shouldn’t be. NDT is the absolute best, but not Armour anymore. It’s been adulterated after Forrest pharm sold it. Wp Thyroid, NP Thyroid, Naturethroid, Erfa, Thiroyd, are all good choices. Adding Cytomel T3 can boost the NDT. It’s trial and error and based solely on your BASAL BODY TEMPERATURE. Keep a thermometer with you and order the book, ‘SOLVED. THE RIDDLE OF ILLNESS. (Langer) It may save you years of misery.

  7. I had my thyroid removed in October 2019 due to several large nodules. Fortunately they were benign. Started taking Levo 137 mcg (T4 only) right after surgery. The first couple of weeks were sort of fine because I still had my own natural hormones flowing thru my body. After 6th week, I began experiencing lots of digestive issues. My Endo ran labs and said my T4 was high and switched me to brand name Synthroid 137 mcg and suggested I skip taking drug on Sundays. Some of the symptoms went away (palpitations, feeling cold) but digestive issues remained. I literally felt like my digestive system slowed to a crawl. My Endo the. Suggested I go see a Gastro. The gastro performed a colonoscopy and said everything was normal. Then CT scan of stomach. Again everything normal. Gastro then prescribed Linzess for constipation and Nortriptyline for anxiety and depression. i am frustrated with the whole experience so far. My quality of life is at an all time low. Help!

  8. I am experiencing hair loss (lots), I am currently taking synthroid. If I switch to Armour, will my hair grow back?

    • colby zethraeus says

      I was losing my hair too, I upped my dosage of and I had more energy and quit losing hair. On the flip side of that at one point I took to much of my levothyroxine and I couldn’t sleep at night and was taking Ambian to sleep. I backed off my dosage and found the happy medium. Good luck I found I am very sensitive to my dosage.

  9. I had my thyroid removed 30 years ago. I was taking synthyroid until about 6 years ago when a natural path prescribed nature thyroid. What a difference! Since it hasn’t been available in my dose for a couple years, I am taking armour. My naturalpath moved and my primary care doctor tells me I don’t need t3 and only checks tsh.
    Is he right? I’m still taking armour at a much higher copay and we agree to disagree every time I see him.
    I’m really frustrated!

    • I’m an RN. Switch doctors if you can, or even better, see a Nurse Practitioner. Your doctor is ignoring your concerns without even confirming with lab tests. Yes, people need T3 as well, and you need to know if your body is converting T4 to T3 well, or if you need a thyroid hormone that includes T3.

      • Anonymous With Hypo says

        I have also heard that because Blue Cross now owns CVS pharmacy they are pushing Synthroid and do not want to cover the other medications. One NP told me that at a recent conference they were told not to prescribe NP Thyroid for hypo due to T3, as it would no longer be covered and quite possibly cost them their license. Welcome to the beginning of Socialized Medicine…where you’re health is ignored and the only thing your insurance company cares about is it’s profit.

    • Sunny L. Payne says

      Your Dr. is brushing you off because he is either uninformed or lazy. I always check the T3 & T4 levels from the lab report because they give you a very clear picture of what your levels are. When anyone begins to talk to me about TSH levels my answer is that they are immaterial, to me, and I then begin to discuss what is really happening and how do I remain stable on my meds.

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