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Scan · levothyroxine

Do iron or soy change Synthroid 50 mcg?

Medically reviewed by Dr. Yuki Tanaka, MD - Clinical pharmacology, Toronto

Last reviewed · 3 min read · Updated

Bone review card, cobalt edge, lime chip: iron tablet far from Synthroid

Yes. Ferrous sulfate and other phosphate binders may bind levothyroxine. Keep Synthroid 50 mcg at least 4 hours from iron. Soybean flour, cottonseed meal, walnuts, and dietary fiber can also bind T4 and cut absorption. Grapefruit juice may delay absorption and reduce bioavailability.

How far from 50 mcg does iron have to sit?

Phosphate binders such as ferrous sulfate, calcium carbonate, sevelamer, and lanthanum may bind levothyroxine. Administer SYNTHROID at least 4 hours apart from these agents.

Morning iron at 7 a.m. with Synthroid at 6 a.m. is a classic silent miss. The blister looks emptied. The TSH still climbs.

If life cannot fit a 4-hour hole, what do clinics do?

Bedtime thyroid with morning iron is a common board fix. Write it once so two alarms stop fighting. Bile-acid sequestrants and ion-exchange resins also want 4 hours or a TSH watch.

Do not start a new iron ritual the same week you change micrograms. Two variables make the next TSH unreadable.

TSH is high and the blister is empty. Blame the maker first?

Look at soy lattes and iron before you blame the manufacturer. That is the usual miss, not a counterfeit 50 mcg.

Doses above 300 mcg a day with a still-high TSH are rarely a need for 400. The insert says think about missed tablets, malabsorption, and drug interactions first.

Does calcium-fortified juice count as iron's cousin?

Fortified juice is mineral plus liquid. It is not water. Read the back of the carton the same week you refill 50 mcg.

Oatmeal and high-fiber breakfasts are the everyday version of the binding problem. Water only in the first half hour. empty-stomach signal rates that breakfast clock.

Which foods does the insert name next to 50 mcg?

Soybean flour, cottonseed meal, walnuts, and dietary fiber may bind and decrease absorption of SYNTHROID from the gut. Grapefruit juice may delay absorption and reduce bioavailability.

Soy drinks in the first hour fail the same rating as a calcium chew. Argue with a paper after the TSH is stable, not on week one of a new 50 mcg.

Is soy infant formula in this adult 50 mcg story?

The pediatric crush line says do not administer the suspension in foods that decrease absorption, such as soybean-based infant formula. Adults do not inherit a chocolate-spread vehicle either.

Kids' crush steps sit on the cut scan. This page stays on iron, soy, fiber, and the 4-hour wall.

Sources

  1. DailyMed SYNTHROID (levothyroxine sodium) tablets, AbbVie
  2. SYNTHROID U.S. prescribing information, AbbVie

Checked against the current label and reviewed by Dr. Yuki Tanaka. See Scan, Tag, Board-check, Post.

Board thread

Answers follow the U.S. Synthroid label.

Dwight F. Psyllium with breakfast, 50 mcg at dawn?

Board reply

Dietary fiber can decrease T4 bioavailability. Take fiber away from levothyroxine. Bedtime thyroid with morning fiber is a common rated fix. Do not start both a fiber ritual and a microgram change in the same week.

Soren B. Prenatal iron at 6:10, Synthroid 50 mcg at 6:00?

Board reply

That is inside the 4-hour wall. Move the prenatal to late morning or move thyroid to bedtime. Recheck TSH after 6 to 8 clean weeks.

Mila K. Soy latte an hour after 50 mcg - still a problem?

Board reply

The labelled breakfast wait is 30 to 60 minutes. Soy protein in that first hour is still a binding risk. After a protected window, soy is food, not a second tablet.