ferrous sulfate vs levothyroxine
Side-by-side comparison of ferrous sulfate and levothyroxine. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
minor Known Drug Interaction
Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine. Drug or Drug Class Effect Phosphate Binders (e.g., calcium carbonate, ferrous sulfate, sevelamer, lanthanum) Phosphate binders may bind to levothyroxine.
Recommendation: Take these two medications at least four hours apart to make sure your thyroid medicine works as it should.
Feosol, Fer-In-Sol
Synthroid, Levoxyl, Tirosint
Ferrous sulfate is an iron supplement. It helps increase iron levels in your body.
Levothyroxine is a medicine that replaces a hormone normally made by your thyroid gland. It is used when the thyroid doesn't make enough hormone on its own.
This medicine is used to relieve hot flashes that occur with headaches. It helps to manage these symptoms. Talk to your doctor if your symptoms do not improve.
This medicine treats hypothyroidism, a condition where the thyroid gland doesn't make enough thyroid hormone. It can be used in adults and children, even newborns. Levothyroxine can also be used after surgery and radioiodine therapy for thyroid cancer to help lower thyroid-stimulating hormone (TSH) levels.
Ferrous sulfate provides iron, which is needed to make red blood cells. Red blood cells carry oxygen throughout your body. By increasing iron levels, this medicine helps your body function properly.
Levothyroxine provides a synthetic form of thyroxine (T4), which is the main hormone produced by the thyroid gland. Your body converts T4 into triiodothyronine (T3), the active form of the hormone. By providing T4, levothyroxine helps restore normal thyroid hormone levels in your body.
- • Fatigue
- • Diarrhea
- • Nausea
- • Headache
- • Pain
- • Fatigue
- • Increased appetite
- • Weight loss
- • Feeling hot
- • Headache
- Tiredness 3,325
- Diarrhea 3,100
- Feeling sick to your stomach 2,746
- Difficulty breathing 2,724
- Death 2,345
- Tiredness 25,847
- Feeling sick to your stomach 22,021
- Head pain 18,798
- Loose stools 18,178
- Difficulty breathing 16,216
No specific warnings noted.
Thyroid hormones, including levothyroxine, should not be used for weight loss or to treat obesity. Using high doses can cause serious and life-threatening side effects, especially when taken with stimulant medicines.
Talk to your doctor before taking this medicine if you are pregnant or breastfeeding. They can help you decide if it is right for you.
Tell your doctor if you are pregnant or plan to become pregnant. Your levothyroxine dose may need to be adjusted during pregnancy. Levothyroxine passes into breast milk, but it is not expected to harm the baby.
How to Read This ferrous sulfate vs levothyroxine Comparison
ferrous sulfate is classified in the Iron Supplement drug class, while levothyroxine sits within the Thyroid Hormone class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are split between OTC and prescription status, which affects access and supervision.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, ferrous sulfate has 14,240 submissions while levothyroxine has 101,060. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known minor interaction flagged in FDA labeling, attributed to ferrous sulfate can stick to levothyroxine in your stomach, which prevents your body from absorbing the thyroid medicine correctly.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between ferrous sulfate and levothyroxine - always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.