Overview

Thyroid hormones come in a variety of formulations and brand names. Synthroid is the most commonly prescribed of all the thyroid supplements. That is because the dose is more reliable than natural products made of dried thyroid glands.

Synthroid is long acting and comes in a wide variety of doses that allows for individualized treatment.

When people develop a sluggish thyroid gland they often feel tired and weak. They may become constipated, sensitive to cold or anemic. They may also suffer with dry skin and hair, thick brittle fingernails and have shortness of breath when they exercise. Some people report clumsiness, weight gain, or puffy eyes.

Thyroid problems are diagnosed with blood tests. The best is one that measures thyroid stimulating hormone, or TSH. This test also helps determine the proper dose of thyroid hormone for treatment.

Side Effects and Interactions

Side effects of thyroid replacement therapy are rare if the dose is appropriate. Specialists recommend beginning treatment with a low dose and gradually increasing it until symptoms of underactive thyroid disappear and the TSH blood test is normal. This may initially require blood tests every four to six weeks and good communication with the doctor.

Signs of overdose include insomnia, heart palpitations, jitteriness, rapid heart beat, increased sweating, higher blood pressure, changes in appetite, and reduced menstrual flow.

Other adverse reactions of excessive thyroid levels include tremor, headache, heart disease, diarrhea, and weight loss. Report any such symptoms to your physician promptly.

A number of medications may interact with Synthroid or alter the tests that detect thyroid problems. People taking estrogen, asthma medicines, decongestants (including those found in over-the-counter cold or flu remedies), antidepressants, certain cholesterol lowering drugs, blood thinners such as Coumadin or heart medicine like digoxin  should check with a physician or pharmacist.

In theory, the herb guggul  might counteract thyroid-suppressing drugs or increase the effect of thyroid hormones. Monitoring thyroid function is prudent. Licorice  may alter the required dose of levothyroxine because of its impact on the thyroid gland.

Never stop taking Synthroid without first checking with your health care provider.

Special Precautions

Too much Synthroid can make a person more susceptible to osteoporosis or weakened bones. You may wish to discuss with your doctor whether you need tests to monitor bone density.

Thyroid replacement is usually needed for the rest of one’s life, and stopping the medicine suddenly could precipitate symptoms of inactive thyroid.

Don’t discontinue Synthroid without your doctor’s supervision.

Taking the Medicine

The usual recommendation is to take Synthroid before breakfast. Although this hormone is probably best taken on an empty stomach, it is more important to take it at the same time every day to maintain a constant level in your body.

Do not take this medication with iron pills, as they can interfere with proper absorption.

Join Over 53,000 Subscribers at The People's Pharmacy

Each week we send two free email newsletters with breaking health news, prescription drug information, home remedies and a preview of our award-winning radio show. Join our mailing list and get the information you need to make confident choices about your health.

  1. rita r.
    south bloomfield,ohio
    Reply

    I have hypothyroidism been taking 100 mcg tabs for over 1 yr. My test results say I am okay, But I feel so depressed that I just stopped functioning. I don’t feel like showering, washing my hair or leaving my house. Being on 100 mcg I definitely do not feel like me. I feel so lazy and withdrawn from all my loved ones. I feel so nervous & scared ! I just want to feel happy again. Someone please understand how I am feeling ! And why?
    Thanks, Rita

    • karen
      Reply

      I am so sorry you are feeling like this, I take 150mg due to having thyroid cancer back in 2009, but can understand how you are feeling, as i too feel exactly the same. I feel everyone around me feel happy while I feel sad and drained all the time. It all gets you down. Luckily my husband has read up on the subject and gives me strength.
      Blood work seems to always come back fine, only people living with thyroid problems are aware of the terrible life you have to live…

  2. Jho
    saudi
    Reply

    Is it ok to take contraceptive pills if I’m also taking Levothyroxine 100mcg tablet? Thank you.

  3. karen
    stockton on tees uk
    Reply

    I had total thyriodectomy in 2009 due to papillary cancer.. I was taking 175mg thyroxine until last week when hospital reduced it to 150mg.

    I was having sever sweats chest pain, confusion… my gp said this was caused by my free T3 being 6.7 and my free T4 being 34… when will I see reduction in my symptoms?

  4. A.M. G.
    Reply

    Dear Sir or Madan, good morning!
    I just want to know if it is safe to take LEVOTHYROXINE with vitamins since I take a lot vitamins.
    Alicia
    People’s Pharmacy response: Wait at least one hour after taking levothyroxine to take any minerals. There is evidence that iron and calcium can interfere with absorption of this hormone, and others might as well. Also, do not take levothyroxine within half an hour of drinking coffee or tea.

  5. Leigh A.
    Reply

    I have been on thyroxine for over thirty years after a thyroidectomy, but I still get some real bad spells that can last for months then I get a few weeks of felling bit more like myself. Is there any herbal teas that could help alongside the thyroxine to help me feel normal?

  6. Lisa See
    Reply

    To Lynn M
    What did the Dr say? I’m having the exact issue. I’m at a loss.
    Thanks Lisa Me

  7. Chris
    Reply

    I have been on levothyroxine for about 20 years. I have been on 100 mcg for about the last 8. The last 6 months or so, I have been having problems with hand tremors, irritability, extreme fatigue (especially after working out) and a 10 pound weight gain. My TSH in January was

  8. kay
    Reply

    I am 68 years old and have been on synthroid since 1990. All these years have gone by and now the doctor keeps changing it every 2 months, up to 175 mg down to 100 and now its been changed 4 or 5 times in the last 8 months. I feel awful, have 3rd stage CKD (chronic kidney disease) and a solitary kidney.
    I am wondering if the medication is interfering with B/P meds even though I have great blood pressure without it. I have to take it for protection of the one kidney. I am at a lose for what to do with the thyroid, I feel weak, tired, one eye has drooped, legs like water. Just this week was put back on the 150 mg. I am at a loss for what to do and just feel like stopping it all together and stop going to the doctor. Thank you.

  9. Erin
    Reply

    How long have you been taking estrogen? The very first thing that I noticed is that you are taking that as well as thyroid medication. Estrogen binds the thyroid hormones and sometimes, people need to have their thyroid medication increased to compensate for that. Also, it causes your lab results to become more unreliable. This means that if your doctor is looking at your tsh alone, they will most likely tell you that you are fine, even if you’re not, and that’s because they’re not taking an in-depth look. Ask for the free t-4/t3 test. With estrogen therapy or birth control pills, test results likely show that you have enough thyroid hormones, but they are binding with the estrogen and are actually not available for use by the body, in which case your free t4 would be low. That would tell your doctor that you in fact DO need an increase of thyroid medication. It can take awhile for you to realise how unwell you actually feel, and now it seems that your “red flag” symptoms are showing themselves.
    Let me add a little personal note here. I have been taking birth control pills (containing estrogen) for quite a few months, maybe half a year, and I was never told that I might need more thyroid medication. I went on with things, thinking I was fine. I was continuously being told that my tsh was fine, good, normal, etc. Then, I got so tired that I couldn’t get out of bed, my hair was falling out, I was very hungry all the time, my feet were numb if I sat down for too long, my legs felt heavy, no energy or desire to do more than sit on the couch. I asked for an increase in my thyroid medicine (I take tirosint) and felt somewhat better, but not yet where I want to be. But, that is indeed the problem, that I need more medication. I can’t say 100% why that happened, but the only change in the past several months has been the ortho tri-cyclen.
    My advice to you is to disregard that tsh number and ask for small increases until you physically Feel better. I had bad experiences with endocrinologists and therefore I get my medication from my regular doctor because he listens to me. Try to see a D.O. if you can because they are sometimes better listeners and are willing to spend more time talking to you. They are trained differently than M.D.’s. I am sure you have known this for a long time, but with thyroid disease you have to tell doctors what you want/need from them and maybe you won’t be their favourite patient for that very reason, but the important thing is that you get what you need to feel better.

  10. seaborne
    Reply

    On Levothyroxine for about eight years, at 1.0 per day. I have steadily been gaining weight, losing my hair, hair breaking off, skin dry and flakey, pain in both lower legs, pain in bottom of feet with some numbness, continuously tired. Am also on Estrogen, Clonidine, Metoprolol, Vitamin D3, chromium, MVI, claritin (for a possible allergy to the clonidine) and B complex. I always wait the 30 minutes to an hour before eating after taking all meds, take meds at same time every day.
    TSH is normal, and that is the only thyroid test my physician routinely draws. Formerly worked for an endocrinologist whose specialty was thyroid, and he did other thyroid tests. I was diagnosed with Hashimoto’s over 18 years ago and was placed on a medication to suppress the thyroid, but I can no longer remember the name. I was to be on it until my thyroid stopped functioning, then given Levothyroxine. It was 10 years before I was placed on a replacement.
    Cholesterol is high, HDL okay, blood pressure suddenly high about five years ago. I have heat intolerance, no problem with cold. Can you give me any advice as to what might be the problem and what I should do. I went to an endocrinologist who was head of the department at a teaching university but his personality was that of a rock at the bottom of the ocean an stopped seeing him. I do not know if we have an endocrinologist now in my area who might be proficient in treating thyroid problems.
    Thank you in advance for your assistance.

  11. Erin
    Reply

    Maybe you are allergic to the fillers in the medication. Have you itched the whole time you’ve taken it and what kind do you take (generic levothyroxine, synthroid, tirosint, armour?) you might want to try tirosint… It’s just made of gelatin, glycerin, water and the active ingredient levothyroxine. It’s a gel capsule, a more pure form of the medication. Just something to consider. Hope this helps.

  12. HD
    Reply

    I have been on 75 mcg and then the doctor switched me to 50 and now I have to take 75 five days a week and 50 two days a week and I am still itching, what is the problem and why can’t it get fixed. I itch my self about every six months so I think my body is adjusting to the medicine and then it switches. What is going on?

  13. K.S:
    Reply

    I am 30 year old woman and was diagnosed slightly hypothyroid with my TSH level at 3.76 so they started me on 50 mcg of levothyroxine last September. I cannot tell you the problems I have suffered due to this drug. I have had terrible vertigo and dizziness, heaviness in my legs predominately my calf muscles, I have been bed ridden for about a month due to orthtostatic blood pressure problems… ( low and high pressure upon standing up ) cannot walk due to terrible pain in calves and vertigo, terrible hot flashes that will NEVER go away, heart palpitations, and it induced some of the worst migraines ever in my life. Before I took this med I was just fatigued and now I feel much much worse. I lost my job due to all these sicknesses… and my doctor said that even though my TSH is now at 2.56 she bumped up my levo dose to 75 mcgs. I told her that I want to switch to Armour. I feel like an old person when I should be out there doing and living my life. I have had various diagnoses through this year of hell. I advise DO NOT TAKE this drug. Find some other alternative to treat your thyroid problems. I am still waiting to feel better and pray that I can get my life back.

  14. James G.
    Reply

    Because they need to see her levels without the meds so they can prescribe the right amount she need. I’m a gulf war vet that had thyroid cancer and it all removed also. This way they can see what exact dose she needs. Don’t tell her but I felt terrible like life was going a hundred mph. And I gained a lot of weight. Was on .75 and they decreased it to .50. Always been around 200 220 but got up to 270 lbs last year. I have to eat very little to stay at 225. I wish you and her good luck. Sgt Green

  15. tiggersmama
    Reply

    yes I to was diagnosed with hyperthyroidism back in 07 and started seeing a endo cause i weighed 102 lbs in 06 and strted losing weight well i went on medication was doing no different till in10 istarted see a new endo and he put me on methemazole and that helped so i kept seeing him had scans done and finally in july of 11 i took the radioactive iodine pill now im hypo and am taking levo50mcg have had no bad side affects but my feet are numb and i get a screaming noise in my head when everything is quiet anyhow i just kept loising weight and now i weigh about 59lbs and im 4ft11in i just cant gain weight im thinking about taking some of those pills they advertise on tv to help you gain weight i also take a multi vit and half of a b6 50 mgs

What Do You Think?

Share your thoughts with others, but be mindful of protecting your own and others' privacy. Not all comments will be posted. Advice from web visitors is not a substitute for medical attention. Do not stop any medicine without checking with the prescriber. In posting a comment, you agree to our commenting policy and website terms and conditions.