Levothyroxine side effects

Levothyroxine Side Effects

Levothyroxine Side Effects – Levothyroxine is the preferred medication of selection for dealing with an underactive thyroid (hypothyroidism).

It’s usually taken for an extended period of time, if not permanently, so there are several essential points you should recognize.

What is Hypothyroidism

Hypothyroidism refers to an underactive thyroid.

It could arise from not enough thyroid hormonal agent manufacturing or since thyroid hormonal agents are suspended prior to they have time to work.

Left neglected it could create several health issues including tiredness, loss of hair, inadequate memory and weight gain.

[su_box title=”Recap” box_color=”#00d408″]In hypothyroidism, the degree of active thyroid hormonal agents is less than what is should preserve healthiness.[/su_box]

What is Levothyroxine Sodium

Levothyroxine sodium is a dental drug used to treat– not heal– hypothyroidism.

Typically just referred to as Levothyroxine, it’s a miracle drug that is naturally similar to T4, a prohormone produced by the thyroid.

Several of the brand name for levothyroxine sodium consist of:

  • Synthroid ®
  • Tirosint ®
  • Unithroid ®
  • Levothroid ®
  • Levo-T ®
  • Levoxyl ®

[su_box title=”Recap” box_color=”#00d408″]Levothyroxine is an artificial prohormone that is used to treat hypothyroidism.[/su_box]

How Levothyroxine Works

How Levothyroxine WorksLevothyroxine is taken by mouth and after that absorbed in the tiny intestine.

Once in the body, levothyroxine (T4) is transformed to triiodothyronine (T3), one of the most energetic thyroid hormone.

Thyroid hormonal agents enhance basic metabolic rate and influence DNA transcription, protein synthesis and also metabolism.

Symptoms of hypothyroidism might reduce after numerous weeks of usage. This indicates a reduction in symptoms such as fatigue, cold, weight gain, hair loss and also damaged memory.

Thyroid-related blood work such as TSH degrees will also go back to regular.

[su_box title=”Recap” box_color=”#00d408″]Taken by mouth, levothyroxine is absorbed in the little intestine and after that converted to the naturally active thyroid hormone T3. Thyroid hormonal agents influence numerous biochemical responses in the body, including metabolic rate.[/su_box]

When to Use Levothyroxine

Levothyroxine treats a number of various kinds of hypothyroidism consisting of:

  • Grown-up hypothyroidism
  • Hereditary hypothyroidism
  • Pregnancy-related hypothyroidism
  • Blood job could find hypothyroidism also when symptoms are not present. This condition is called subclinical hypothyroidism.

Some professionals advise not recommending levothyroxine to deal with subclinical hypothyroidism due to the high threat of serious adverse effects.

[su_box title=”Recap” box_color=”#00d408″]Levothyroxine is used to deal with hypothyroidism in kids, grownups and also expecting women. It’s frequently not recommended in situations of subclinical hypothyroidism, when no symptoms exist.[/su_box]

Levothyroxine Side Effects

The majority of side effects from levothyroxine come from dosages that are greater than necessary.

Exceedingly high doses could take place because of levothyroxine’s slim healing window. This indicates there is a small distinction in between having inadequate as well as too much levothyroxine.

Much Less Usual

  • difficult or struggled breathing
  • fainting.
  • fast, slow, uneven, battering, or competing heart beat or pulse.
  • high temperature
  • trouble with swallowing
  • dilated neck capillarie
  • severe fatigue
  • irregular breathing.
  • irritation.
  • menstruation changes.
  • nausea.
  • warmth intolerance.
  • upper body discomfort or discomfort
  • lowered pee result
  • hives or welts.
  • enhanced high blood pressure.
  • boosted pulse.
  • discomfort or pain in the arms, jaw, back, or neck.
  • lack of breath.
  • rigidity in the upper body.
  • tremors.
  • bothered breathing.
  • skin itching, breakout, or inflammation.
  • sweating.
  • swelling of the eyes, face, lips, throat, or tongue.

More Common

The more common side effects of levothyroxine could include:

  • too much sweating.
  • headache.
  • attention deficit disorder.
  • anxiety.
  • impatience.
  • state of mind swings.
  • fatigue.
  • boosted appetite.
  • weight loss.
  • warm level of sensitivity.
  • hair loss (usually short-term).
  • diarrhea.
  • vomiting.
  • belly cramps.
  • sleeplessness (trouble sleeping).
  • tremblings.
  • muscular tissue weak point.
  • menstrual irregularities.

If these effects are moderate, they might go away within a couple of days or a few weeks. If they’re much more severe or do not go away, talk with your medical professional or pharmacologist.


  • absence or slowing of normal growth in children.
  • limp or walk preferring one leg.
  • Blurred or dual vision.
  • dizziness.
  • eye discomfort.
  • serious headache.
  • discomfort in the hip or knee.
  • seizures.


  • Cardiac arrest. Symptoms can include:.
    – upper body discomfort.
    – shortness of breath.
    – pain in your top body.
  • Cardiac arrest. Symptoms could consist of:.
    – lack of breath.
    – extreme fatigue.
    – swelling in your legs, ankles, or feet.
    – unanticipated weight gain.
  • Extremely quick heart price.
  • Irregular heart rhythm.

[su_box title=”Recap” box_color=”#00d408″]If utilizing expensive a dose, levothyroxine could create various adverse effects. Sometimes, levothyroxine could cause serious heart, allergic reaction and also neurological symptoms.[/su_box]

Symptoms of Overdose

  • modification in consciousness.
  • chilly, clammy skin.
  • impaired thinking.
  • loss of awareness.
  • sudden frustration.
  • unexpected loss of coordination.
  • unexpected slurring of speech.
  • confusion.
  • disorientation.
  • quick or weak pulse.

Some side effects could happen that normally do not need medical interest. These Levothyroxine side effects may go away during treatment as your body gets used to the medicine.

Likewise, your healthcare specialist might have the ability to tell you regarding methods to prevent or lower several of these side effects.

Check with your healthcare specialist if any of the complying with negative effects continue or are aggravating or if you have any type of questions concerning them:.

Less common

  • sensation not well or dissatisfied.
  • sensation of pain.
  • feeling of warmth.
  • sensation things are unreal.
  • feelings of suspicion and also mistrust.
  • hair loss.
  • stomach or tummy pains.
  • modification in appetite.
  • sobbing.
  • looseness of the bowels.
  • false or unusual sense of health.
  • concern.
  • restlessness.
  • trouble getting pregnant.
  • trouble sitting still.
  • unusual exhaustion or weakness.
  • throwing up.
  • weight gain.
  • weight loss.
  • migraine.
  • enhanced hunger.
  • psychological clinical depression.
  • muscle mass weakness.
  • uneasiness.
  • fast to react or overreact psychologically.
  • quickly altering state of minds.
  • inflammation of the face, neck, arms, and periodically, top chest.

Opposite effects not listed might also take place in some people. If you notice any other effects, contact your health care professional.

Levothyroxine Interaction

Various Other Drugs

  • Oral Tablet. Levothyroxine could interact with other medications, vitamins, or herbs you might be taking. An interaction is when a material transforms the method a drug works. his can be damaging or stop the drug from functioning well. Levothyroxine likewise has significant communications with some medications, including.
  • Ciprofloxacin.
  • Orlistat.
  • Ritonavir.
  • Antacids.

Levothyroxine could raise the level of blood slimmers, leading to a better risk of blood loss.

It could additionally decrease the degree of particular heart medications such as digoxin, which can create damaged cardiac function.

Food Interactions

Levothyroxine can communicate with both food and other medications.

For this reason it ought to be tackled an empty belly in the early morning or night. No food must be consumed one hour either side of when it was taken.

Also note that foods like soybeans, walnuts as well as nutritional fiber reduce its absorption.

[su_box title=”Recap” box_color=”#00d408″]Make certain to talk about drug and food interactions with your medical professional and pharmacologist prior to beginning levothyroxine.[/su_box]

Interactions that Boost the Risk of Levothyroxine Side Effects

Taking levothyroxine with certain drugs may result in a boost in negative effects. Examples of these drugs include:

Antidepressants such as amitriptyline, maprotiline, and sertraline.

The side effects of both the antidepressants and also levothyroxine could boost when you take these drugs with each other. This could place you in jeopardy for uneven heart rhythms (arrhythmias).

Sympathomimetic drugs such as pseudoephedrine and albuterol.

The effects of both the sympathomimetic drugs and also levothyroxine could enhance when you take these drugs with each other. This might put you at risk of severe heart issues.

Blood slimmers such as warfarin.

Taking these drugs with levothyroxine may raise your threat of bleeding. Your medical professional could should reduce the dose of your blood thinner if you are also taking levothyroxine.


Taking this drug with levothyroxine could boost your threat of hypertension and quick heart price.

Interactions that Could Make Your Drugs Much Less Effective

When Levothyroxine is Less Effective

When you take levothyroxine with particular drugs, it may not function too to treat your condition. This is since the quantity of levothyroxine in your body could be reduced. Examples of these drugs consist of:

  • Rifampin and also anti-seizure drugs such as carbamazepine and phenobarbital.
  • Calcium carbonate or ferrous sulfate. Take levothyroxine a minimum of 4 hrs prior to or after taking these drugs in order to help ensure that levothyroxine works effectively.
  • Colesevelam, cholestyramine, colestipol, kayexalate, or sevelamer. Take levothyroxine a minimum of 4 hrs before taking these medications in order to help see to it that levothyroxine works appropriately.
  • Orlistat.
  • Simethicone and antacids such as aluminum or magnesium.
  • Cancer cells drugs that come from the tyrosine-kinase inhibitors course, such as imatinib.

When Various Other Drugs are Much Less Effective:

When certain drugs are utilized with levothyroxine, they could not function as well. This is since the quantity of these drugs in your body might be reduced. Instances of these drugs include:

  • Drugs to treat diabetic issues, such as insulin, metformin, nateglinide, glipizide, and also pioglitazone. If you take any of these diabetes drugs with levothyroxine, your medical professional might have to enhance your dosage of these drugs.
  • Digoxin. If you take it with levothyroxine, your doctor might have to raise your dosage of digoxin.
  • Theophylline. Your medical professional might monitor the levels of theophylline in your body if you take it with levothyroxine.

Levothyroxine Warnings

[su_note note_color=”#ff032b” text_color=”#ffffff”]CAUTION: NOT FOR THERAPY OF WEIGHT PROBLEMS OR FOR WEIGHT MANAGEMENT Thyroid hormones, consisting of Levothyroxine sodium tablet computers, either alone or with various other restorative agents, must not be made use of for the therapy of obesity or for weight management.[/su_note]

In euthyroid individuals, doses within the variety of day-to-day hormone needs are ineffective for weight decrease.

Larger dosages could generate major and even harmful symptoms of toxicity, particularly when given in association with sympathomimetic amines such as those made use of for their anorectic effects.

People with heart issues

Levothyroxine can boost your threat of serious heart issues, such as cardiac arrest, abnormal heart rhythm, and heart failure. This danger is boosted if you’ve already had these troubles. Tell your doctor if you have heart problems or a background of heart problems. Your medical professional may choose to begin you on a reduced dose.

Individuals with diabetes

Allow your physician understand if you have diabetes. Taking levothyroxine can make your diabetes worse. Your doctor might check your blood sugar degree a lot more very closely while you take this drug as well as readjust your diabetes drugs if needed.

People with osteoporosis

Utilizing levothyroxine for a long period of time can cause decreases in your bone mineral thickness and place you at higher threat of bone cracks.

People with adrenal or pituitary gland issues

Let your physician understand if you have any type of adrenal or pituitary gland issues. Utilizing levothyroxine could cause adjustments to your degrees of thyroid hormone that can make these issues worse.

Individuals with blood clot conditions

Allow your doctor recognize if you have any kind of blood clot disorders. Taking levothyroxine could make it harder for your blood to clot as well as make hemorrhaging more probable.

Expecting women

Levothyroxine is a classification A maternity drug. That indicates 2 things:

  • Studies of the drug in expecting women haven’t shown risk to the fetus.
  • The drug needs to only be used while pregnant if plainly required.

Talk to your physician if you’re expecting or intending to end up being pregnant. It appears not likely that this drug will certainly harm an unborn child.

Nevertheless, this drug ought to just be utilized during pregnancy if plainly required.

Women who are breast-feeding

Small amounts of levothyroxine could pass into breast milk, but this drug is typically risk-free to take while breast-feeding. Speak with your doctor about the most effective way to feed your kid while taking levothyroxine.

For senior citizens

If you’re older than 65 years, you could go to higher danger of establishing negative heart effects (such as irregular heart rhythms) while taking this drug. Your doctor may prefer to begin you on a lower dosage.

For kids

Levothyroxine has just been accepted for use in kids for the therapy of hypothyroidism.

The tablet could be utilized safely in youngsters of any ages. The capsule can be made use of securely in children older compared to 5 years.


Levothyroxine could trigger a severe allergic reaction. Symptoms can include:

  • skin rash or hives
  • flushing.
  • swelling of your face, lips, throat, or tongue.
  • trouble breathing.
  • hissing.
  • tummy discomfort.
  • queasiness.
  • throwing up.
  • looseness of the bowels.
  • fever.

If you have an allergy, call your doctor or regional poison control center as soon as possible.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it once more can be deadly (reason death).

How to Take Levothyroxine (Dose)

All feasible doses as well as drug types might not be included below. Your dose, drug type, and how typically you take the drug will certainly depend on:.

  • your age.
  • the problem being dealt with.
  • how serious your problem is.
  • various other clinical problems you have.
  • how you respond to the initial dosage.


Dosage Forms & Strengths



– 25mcg, 50mcg, 75mcg, 88mcg, 100mcg, 112mcg
– 125mcg, 137mcg, 150mcg, 175mcg, 200mcg, 300mcg

Capsule (Tirosint)

– 13mcg, 25mcg, 50mcg, 75mcg, 88mcg.
– 100mcg, 112 mcg, 125mcg, 137 mcg, 150mcg.

Oral Solution (Tirosint-SOL)

– 13mcg/mL, 25mcg/mL, 50mcg/mL, 75mcg/mL, 88mcg/mL.
– 100mcg/mL, 112mcg/mL, 125mcg/mL, 137mcg/mL, 150mcg/mL.
– 175mcg/mL, 200mcg/mL.

Powder for Injection

– 100mcg/vial.
– 200mcg/vial.
– 500mcg/vial.


Mild Hypothyroidism

1.7 mcg/kg or 100-125 mcg PO qDay; not to go beyond 300 mcg/day.

– 50 years (or <50 yr with CV disease).

  • Usual initial dose: 25-50 mcg/day.
  • May adjust dose by 12.5-25 mcg q6-8Week.

– 50 years with Curriculum Vitae disease.

  • Normal preliminary dosage: 12.5-25 mcg PO qDay.
  • Might adjust dose by 12.5-25 mcg q4-6weeks up until patient ends up being euthyroid and also product TSH focus normalized;
    adjustments q6-8weeks additionally utilized.
  • Dosage variety: 100-125 mcg PO qDay.

Severe Hypothyroidism

  • First: 12.5-25 mcg PO qDay.
  • Adjust dosage by 25 mcg/day q2-4Week PRN.

Subclinical Hypothyroidism

Preliminary: 1 mcg/kg PO qDay may be adequate. If replacement treatment not launched, screen individual annually for clinical status.

Myxedema Coma

300-500 mcg IV as soon as, AFTER THAT 50-100 mcg qDay up until patient is able to tolerate dental management; might consider smaller doses in individuals with cardiovascular disease.

Body Organ Preservation (Orphan)

Conservation of body organ function in brain-dead body organ contributors.

Orphan indicator sponsor.

  • Fera Pharmaceuticals, LLC; 134 Birch Hillside Roadway; Grasshopper Valley, NY 11560.

Dosing Factors to Consider

Lower dosage of Tirosint pills might be called for compared to typical T4 tablets for hypothyroidism in individuals with damaged stomach acid secretion to reach their target TSH levels; Tirosint has actually revealed enhanced absorption compared to traditional T4 tablet computers.

Look for bioequivalence if changing brands/generics, OR weekly after switching from one levothyroxine sodium prep work to one more.
Display lotion thyroid levels; individual may be asymptomatic.


  • At first examine people q6-8Week.
  • Once normalization of thyroid feature as well as product TSH conc attained, examine q6-12mo.



Dosage Forms & Strengths

– 25mcg, 50mcg, 75mcg, 88mcg, 100mcg, 112mcg.
– 125mcg, 137mcg, 150mcg, 175mcg, 200mcg, 300mcg.

Capsule (Tirosint)

– 13mcg, 25mcg, 50mcg, 75mcg, 88mcg.
– 100mcg, 112 mcg, 125mcg, 137 mcg, 150mcg.

Oral remedy (Tirosint-SOL)

– 13mcg/mL, 25mcg/mL, 50mcg/mL, 75mcg/mL, 88mcg/mL.
– 100mcg/mL, 112mcg/mL, 125mcg/mL, 137mcg/mL, 150mcg/mL.
– 175mcg/mL, 200mcg/mL.

Powder for Injection

– 200mcg/vial.
– 500mcg/vial.


Age 1-3 months

  • 10-15 mcg/kg/day PO.
  • 5-7.5 mcg/kg/day IV/IM.
  • Usage lower starting dose (25 mcg/day) if client in jeopardy of cardiac failing; if first lotion T4 lower than 5 mcg/dL start therapy at greater dose (50 mcg/day).

Age 3-6 months

  • 8-10 mcg/kg/day PO, OR.
  • 25-50 mcg/day PO.
  • 4-7.5 mcg/kg/day IV/IM.

Age 6-12 months

  • 6-8 mcg/kg/day PO, OR.
  • 50-75 mcg/day PO.
  • 3-6 mcg/kg/day IV/IM.

Age 1-5 years

  • 5-6 mcg/kg/day PO, OR.
  • 75-100 mcg/day PO.
  • 2.5-4.5 mcg/kg/day IV/IM.

Age 6-12 years

  • 4-5 mcg/kg/day PO, OR.
  • 100-125 mcg/day PO.
  • 2-3.75 mcg/kg/day IV/IM.

12 years

  • 2-3 mcg/kg/day PO, OR.
  • 150 mcg/day PO.
  • 1-2.25 mcg/kg/day IV/IM.

Dosing considerations

  • Look for bioequivalence if changing brands/generics.
  • Could decrease hyperactivity in older kids by initiating dosage at 1/4 of recommended dosage; rise by that quantity every week up until full dose achieved.
  • Begin kids with serious or chronic hypothyroidism at 25 mcg/day; change dose by 25 mcg qweek.


US Boxed Warning

Thyroid hormones, either alone or with various other agents, need to not be made use of for the treatment of obesity or for weight reduction.

In euthyroid people, doses within the series of daily hormone needs are inadequate for weight decrease. Bigger doses could generate severe or perhaps life threatening manifestations of toxicity, particularly when given in organization with sympathomimetic amines such as those utilized for their anorectic effects.

Narrow Therapeutic Index

This drug ought to be taken into consideration a narrow therapeutic index (NTI) drug as tiny distinctions in dosage or blood focus may cause severe therapeutic failures or damaging drug responses.


  • Common substitution should be done very carefully, if in any way, as existing bioequivalence standards are normally inadequate for NTI drugs.
  • Added and/or a lot more constant surveillance must be done to make certain receipt of an effective dose while preventing unneeded toxicities.

Speak with WARNINGS area for additional precautions.


Hardly any drug is eliminated by dialysis due to the fact that T4 is very protein bound.

What Happens If Levothyroxine Doesn’t Work?

Levothyroxine is taken into consideration the preferred treatment for hypothyroidism.

Nevertheless, approximately 10 to 20% of individuals with hypothyroidism do not have a complete action to levothyroxine. This might result from:

  • Missed doses.
  • Diseases that disrupt levothyroxine absorption (e.g., celiac disease).
  • Effect of other autoimmune illness related to hypothyroidism (e.g., type I diabetes mellitus and lupus).
  • Drug interactions.
  • As a result of the danger of poisoning, medical professionals will not prescribe greater doses of levothyroxine.

T3 Combination or Desiccated Thyroid

When the reaction to levothyroxine isn’t really sufficient, medical professionals might consider combining it with L-triiodothyronine (a synthetic kind of T3).

This is taken into consideration an experimental therapy though.

Another choice is desiccated thyroid hormone essence (DTE), an all-natural item originated from the thyroid glands of cows or pigs (20 ).

In one study of DTE, 48.6% of the 70 grown-up individuals preferred how they really felt on that drug as compared to levothyroxine. The DTE team also showed an average weight loss of three extra pounds (21 ).

Nonetheless, excessive amounts of T3 have been discovered in some batches of desiccated thyroid, elevating issues concerning its usage.

Additionally, desiccated thyroid has not been shown to be as risk-free or reliable as levothyroxine in the therapy of hypothyroidism. Consequently, levothyroxine stays the drug of option for handling an underactive thyroid. (9, 22).

But you could constantly request desiccated thryoid with your physician if levothyroxine is not working for you.

[su_box title=”Recap” box_color=”#00d408″]Levothyroxine is the therapy of option for hypothyroidism. Other therapy choices, consisting of using T3 or desiccated thyroid hormone are not advised.[/su_box]

Levothyroxine Side Effects Conclusion

Our goal is to give you with the most pertinent and also present information. Nonetheless, because drugs impact each person in different ways, we can not ensure that this info consists of all possible Levothyroxine side effects.

This info is not a replacement for clinical guidance. Constantly discuss feasible adverse effects with a doctor who understands your case history.

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