Compare Synthroid vs. Armour Thyroid

Head-to-head comparisons of medication uses, side effects, ratings, and more.

Replaces thyroid hormones.

Synthroid (Levothyroxine) is an important replacement hormone when your body can't make enough thyroid hormone. It's easily affected by food, other medicines or supplements, and health conditions, so you should try to take it exactly as instructed.

4.1/ 5 average rating with 1090 reviewsforSynthroid
Replaces thyroid hormones.

Armour Thyroid (thyroid desiccated) can be used to treat low thyroid hormone for some people, but it's not the first-choice treatment for this condition.

  • Supplies an essential hormone that your body needs to function. Works well to improve symptoms of an underactive thyroid.
  • Safe to use for any age range and pregnant women.
  • Cheap.
  • Armour Thyroid (thyroid desiccated) is derived from an animal source (pigs), so it's considered natural.
  • Available in cheaper generic form.
  • Even though Armour Thyroid (thyroid desiccated) isn't a first choice recommendation, some people feel better on this medicine compared to other thyroid hormone medications.
  • Absorption is easily affected by food and other medicines.
  • Not one-dose-fits-all: Dose adjustments are usually needed when starting the medicine and when your health changes.
  • Routine blood tests are needed at least yearly and more during dose adjustments, but it takes a long time to see full effect (6 to 8 weeks).
  • Different brands of Levothyroxine may not work the same. Ask your pharmacist if your refill looks different than your old pills. Synthroid is one of the few drugs where the brand really does work better than the generic for many people.
  • Lots of drug interactions, so check with your pharmacist before taking anything new.
  • Armour Thyroid (thyroid desiccated) is not recommended by doctors and the American Thyroid Association because of the inconsistent amounts of thyroid hormone in each tablet and the lack of research studies.
  • FDA does not approve Armour Thyroid (thyroid desiccated); they have not found this medicine to be safe and effective.
  • Not recommended for elderly people.
Used for
Dosage forms
  • Pill
  • Pill
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1090 reviews so far
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Side effects
The Synthroid (Levothyroxine) FDA package insert doesn’t have numbers about how common side effects are.
The Armour Thyroid (thyroid desiccated) FDA package insert doesn’t have numbers about how common side effects are.
Risks and risk factors
  • Heart problems
    • Current heart disease
    • Age 60 or older
    • Taking Synthroid (Levothyroxine) with certain types of stimulant medicines
  • Weight reduction
  • Drug interactions
  • Bone effects
    • Duration of treatment
    • Postmenopausal women
  • Lack of adrenal function
See more detailed risks and warnings
  • Overdose of thyroid hormone
    • Taking other drugs for weight loss
  • Changes in blood sugar
    • Diabetes
  • Changes in blood clotting
    • Taking blood thinners
  • Risk of contamination
  • Increased risk of heart problems
    • Angina
    • Elderly
See more detailed risks and warnings