29 Medications That May Cause Adverse Interactions with Thyroid Drugs

Buy Lab Tests Online

Nelson Vergel

Founder, ExcelMale.com
The thyroid medication levothyroxine (LEVO-T, LEVOXYL, NOVOTHYROX, SYNTHROID, THYRO-TABS, UNITHROID) is used to treat hypothyroidism, an endocrine disorder resulting from a thyroid homone deficiency that affects about 4.6 percent of the U.S. population. The medication is used to replace the missing or deficient amount of thyroid hormone. The number of prescriptions for levothyroxine filled each year—more than 75 million U.S. prescriptions in 2007 — makes it one of the most prescribed drugs in the country.

Unfortunately, the use of other medications while taking levothyroxine could have one of several kinds of unintended results:
• Certain medications can decrease the absorption of levothyroxine resulting in lower levels in the blood.
• Other medications can increase the rate at which the body gets rid of levothyroxine, also resulting in lower thyroid levels in the blood.
• Other medications can cause changes of levothyroxine binding in blood
• Levothyroxine can affect the safety or effectiveness of other medications by raising or lowering the levels of these other drugs in the blood.

Worst Pills
thyroid med interactions.jpg
Last edited:
Defy Medical TRT clinic doctor

Vettester Chris

Super Moderator
Actually, these are good reasons to get on Natural Dessicated Thyroid medications (NDT), as oposed to Levothyroxine. You will notice in a lot of cases that these medications state they basically have an "effect" on the productivity and effectiveness of Levothyroxine, which is a synthetic form of thyroxine; T4 Only medication. NDT is natural extract from pigs, and provides not only natural thyroxine, but it also adds T3, T2 & T1, just as our own thyroids produce. If Levothyroxine is somehow being deemed "ineffective", then basically that's telling me it's not converting to T3, which is what you ultimately need for energy (ATP).

Regardless, some medications could still adversely interact in other areas (adrenals, kidneys, enzymes, etc.), which could still contribute to the productivity of thyroid activity, but that's quite different that a direct attachment to Levothryoxine, which is taken out of the equation when NDT is presented.
Last edited:

Dave Barry

Typically, multi-vitamins should not be taken within 2-3 hours of thyroid medication. "Additionally, taking thyroid with a fiber supplement reduces absorption so it should be taken 2-3 hours before taking a fiber supplement or at least 4 hours after taking the supplement." Understanding Pharmacology, Workman, LaCharity, and Kruchko P.420.
Read on stopthethyroidmadness that some folks crush and take NDT sublinguily. Anyone know if that truly works? If so it should help bypass any issues with absorbtion due to competing supplements.

Dave Barry

Some thyroid medication such as Nature-Throid and Armour (as compared to Synthroid) are more conducive to crushing/chewing since they are softer and have no coating. It will be absorbed faster sublingually (some people claim they need less medication) if you keep it under your tongue for 10-15min (I am guessing the time). However, you will end up swallowing some of the tablet so you will still run into absorption competition with the meds/vitamins/fiber as listed above. Personally, I would not take the chance, unless several studies showed it made no difference (mixing with Nelson's list) as well as my blood-work boar out no difference. Also, if you are going to crush your thyroid medication (manufacture's do not recommend it), you should do it all the time so it's apparent through blood-work that you are using the correct dosage. Finally, since Armour has a very short half-life (Dr. Mercola suggests splitting dosage and taking 2x/day), crushing it will only shorten (due to faster absorption) it more so you'd be better off crushing Nature-Throid, since it has a longer half-life, if you are going to experiment imo.

Last edited:
Folks - been about two weeks on naturethroid - only 1/4 grain. I feel a little more jittery, temp up, but more pain in the thyroid. Stabbing pains, dull pains, nodule that hurts more, voice that occasionally goes hoarse. Is this typical as i adjust?

Dave Barry


Considering the small amount of thyroid you are using, the effects you are feeling seem over-the-top. If nothing else, make sure that you get the appropriate blood-work within 30 days. Regardless, you may want to contact your doctor asap.
Thanks Dave - I was leaning more towards a natural progression of whatever is going on with my thyroid versus a reaction to the meds. Thanks for your response.


Armour NDT
My DR. started me on a 4 day ramp-up by a small (15mg) day one and adding one more each day until on day 4 I was taking one big (60mg).
Then next week it was big (60mg) and small (15mg) for a week and titrated up by a small (15mg) each week watching symptoms. I ended up on 2 big and 3 small (165mg) of Armor a day.
Directions were to take in the AM on an empty stomach with water and no food or meds for at least an hour. I get up an hour before I get up and take a piss and meds and then back to bed for an hour till I get up for work. I get better than an hour with nothing else in my stomach to interfere with absorption of the NDT.
does carnitine effect the absorption of thyroid meds? i believe i have read that carnitine can be used to help with "hyper" thyroid issues so to that regard i am thinking it may not be a good thing to take with thyroid meds? any one know for sure? thanks!

Nelson Vergel

Founder, ExcelMale.com
Carnitine in muscle decreases with hyper and hypothyrodism:


Weakness is common in both hyper- and hypothyroidism, and skeletal muscle l-carnitine may play a role in this regard, as suggested by studies indicating abnormal levels of carnitine in serum and urine of patients with thyroid dysfunction. Skeletal muscle samples were obtained for carnitine analysis from control subjects, and from hyperthyroid and hypothyroid patients before and after treatment. There was a significant reduction in carnitine, especially the esterified portion, in hyperthyroid individuals, with a return to normal as euthyroid status was regained. In hypothyroid patients, there was a trend for carnitine to be lower than normal and for improvement once euthyroid status was attained. Our data indicate that muscle carnitine levels are affected by both hypo- and hyperthyroidism. A decrease in muscle carnitine in both conditions may contribute to thyroid myopathy. Muscle Nerve, 2005

Carnitine can also affect how thyroid hormones work in tissue (this may be great for hyperthyroidism but not for hypothyroidism)

Abstract: By experiments on cells (neurons, hepatocytes, and fibroblasts) that are targets for thyroid hormones and a randomized clinical trial on iatrogenic hyperthyroidism, we validated the concept that l-carnitine is a peripheral antagonist of thyroid hormone action. In particular, l-carnitine inhibits both triiodothyronine (T3) and thyroxine (T4) entry into the cell nuclei. This is relevant because thyroid hormone action is mainly mediated by specific nuclear receptors. In the randomized trial, we showed that 2 and 4 grams per day of oral l-carnitine are capable of reversing hyperthyroid symptoms (and biochemical changes in the hyperthyroid direction) as well as preventing (or minimizing) the appearance of hyperthyroid symptoms (or biochemical changes in the hyperthyroid direction). It is noteworthy that some biochemical parameters (thyrotropin and urine hydroxyproline) were refractory to the l-carnitine inhibition of thyroid hormone action, while osteocalcin changed in the hyperthyroid direction, but with a beneficial end result on bone. A very recent clinical observation proved the usefulness of l-carnitine in the most serious form of hyperthyroidism: thyroid storm. Since hyperthyroidism impoverishes the tissue deposits of carnitine, there is a rationale for using l-carnitine at least in certain clinical settings.


New Member
Anyone go from straight T3 to NDT and feel better? Currently on 10mcg t3 twice per day, no complaints but I wonder if I would feel different if I switched to NDT.

Vettester Chris

Super Moderator
Anyone go from straight T3 to NDT and feel better? Currently on 10mcg t3 twice per day, no complaints but I wonder if I would feel different if I switched to NDT.

I have experience with both medications. You "could" see some better results with going NDT, as many know I'm a proponent of it. However, implementing NDT now also implements T4 into the mix, so there are other variables in play. One main one will be ensuring that T4 is converting adequately to T3, and not excessively converting to Reverse T3. I would make sure your cortisol is where it needs to be, and make sure iodine and selenium is supplemented if needed.

As far as doing the actual switch ... If it were me, the first week, I would drop 10mcg of the T3 each day and add 1 grain of NDT. Keep in mind, one (1) grain of NDT right off the bat will have approx. 9 to 10mcg of T3. You will want the first week of NDT to get T4 built up a bit and converting down to T3. See where you're at and how you feel after the first week. The one grain (60mcg) of NDT will play out to equal approx. 25mcg of Cytomel (give or take a few mcgs). At that point you should be able to transition off the T3 Cytomel completely.

You will not only want to base this with how you feel, but you will want to run labs after about a month. You will want to see FT4, FT3, Reverse T3, and throw a TSH in as well. If you haven't run antibodies, then run them (TPO & TgAb). IF they have been checked, no worries. We will want to see how the close the FT4 & FT3 labs are together in their respective reference ranges, and compare the ratio with FT3 & RT3. To reiterate, depending on how you're feeling, this is where you might want to titrate your dosage up (can't imagine it going down), and/or possible addition of a little T4 is added, since the ratio of T4 to T3 is different with NDT's than what the actual human thyroid would produce naturally.

It's a gradual process of titration to get to where you feel just right, and your lab values are where you want them. I'd suggest stepping up a 1/2 grain when doing this."Most" cases, you might want to be shooting for 50% to 80% of the reference range value with both FT4 and FT3, and aiming to keep Reverse T3 at a respectable ratio compared to FT3; usually > 20.

If you don't feel better, or even start feeling worse, RT3 could very well be the culprit. Labs will tell you what's going on, and they will also be a marker to look at other areas like cortisol, iron & ferritin, B12, D3 & electrolytes "if" you are experiencing issues, or inconsistent patterns with your well being related to your treatment program.
Last edited:

Vettester Chris

Super Moderator
Keep in mind, this is just a discussion forum. There's a multitude of ways to treat hypothyroidism, and what works for one might not work for the other. Chaps, you know T3-Only appears to provide positive results. You can always fall back on that if all else fails. However, at 20mcg/day of T3, you might be able discover some untapped improvements with your thyroid program. Some people do 4 grains/day and feel on top of the world. Like testosterone, it's a little different for everyone ...
Buy Lab Tests Online


bodybuilder test discounted labs
Defy Medical TRT clinic
nelson vergel coaching for men
Discounted Labs
cheap hcg viagra cialis
TRT in UK Balance my hormones
Testosterone books nelson vergel
Register on ExcelMale.com
Trimix HCG Offer Excelmale
Thumos USA men's mentoring and coaching
Testosterone TRT HRT Doctor Near Me
how to save your marriage

Online statistics

Members online
Guests online
Total visitors

Latest posts