Synthroid interactions: What to avoid for safe use
Does Synthroid interact with supplements that may help with arthritis, such as ashwagandha, collagen, or turmeric? Synthroid is not known to interact with these supplements., Ashwagandha is used to ease symptoms of various health conditions, including arthriti
Does Synthroid interact with supplements that may help with arthritis, such as ashwagandha, collagen, or turmeric?
Synthroid is not known to interact with these supplements., Ashwagandha is used to ease symptoms of various health conditions, including arthritis, stress, and anxiety. Collagen supplements are used to improve skin and joint health. Turmeric may be used to reduce inflammation, ease pain, and improve digestion., To learn more about Synthroid and these supplements, talk with your doctor or pharmacist. They can advise you on whether it’s safe to take any of them during Synthroid treatment.
Do B vitamins such as biotin or B12 interact with Synthroid?
No, Synthroid does not directly interact with B vitamins such as biotin and vitamin B12. However, biotin supplements may cause inaccurate thyroid hormone test results. This includes tests for thyroid-stimulating hormone (TSH) and thyroxine (T4)., If you take a biotin supplement, be sure to tell your doctor. They’ll likely ask you to stop taking this supplement at least 2 days before they run any thyroid hormone tests.
Is it safe to take Synthroid with Benadryl?
Yes, it’s believed that Synthroid is safe to take with diphenhydramine (Benadryl), an antihistamine used to treat conditions such as seasonal allergies. Synthroid and Benadryl are not known to interact with each other., If you’re interested in an allergy treatment while taking Synthroid, talk with your doctor or pharmacist.
Key takeaways
- Synthroid (levothyroxine) can interact with many medications, supplements, and foods that may make it less effective. These include antacids, calcium and iron supplements, birth control containing estrogen, certain seizure medications, and foods like coffee, walnuts, and grapefruit.
- With untreated adrenal insufficiency, Synthroid speeds up how rapidly your body breaks down cortisol, which can trigger a potentially fatal adrenal crisis, so treatment for adrenal insufficiency is needed before starting Synthroid.
- To help Synthroid work effectively, take it on an empty stomach at least 30 minutes to 1 hour before eating, and separate it by at least 4 hours from antacids, calcium or iron supplements, and certain other medications that can interfere with absorption.
Synthroid (levothyroxine) is a brand-name oral tablet used as a thyroid hormone replacement therapy to treat some types of hypothyroidism. Doctors may also prescribe it in combination with certain other thyroid cancer treatments. Synthroid is approved for these uses in adults and children of any age.
An interaction occurs when one substance causes another substance to have a different effect than expected.
In some cases, a factor or condition could prevent your doctor from prescribing Synthroid due to the risk of harm. (This is known as a contraindication.)
Doctors typically will not prescribe Synthroid if you have untreated adrenal insufficiency. With this condition, your body does not produce enough cortisol. Synthroid increases how rapidly your body breaks down and clears out cortisol. If your adrenal insufficiency is untreated, taking Synthroid can dangerously accelerate this process and trigger a potentially fatal adrenal crisis.
If you have adrenal insufficiency, your doctor may give you treatments for your condition before you start taking Synthroid.
Note: Before you start treatment with Synthroid, it’s important to tell your doctor if this contraindication applies to you. They can determine whether to prescribe Synthroid.
There’s not a known interaction between Synthroid and alcohol. If you drink alcohol, talk with your doctor about how much, if any, is safe to consume during treatment with this medication.
Before starting Synthroid, tell your doctor and pharmacist which prescription, over-the-counter, and other drugs you take. Discussing this information with them may help you avoid possible interactions.
Doctors may not prescribe the following medications with Synthroid as they may cause an interaction. Keep in mind that this chart does not include all drugs that may interact with Synthroid. (Some of these interactions are described in detail in the “Drug interactions in depth” section.)
Here’s a closer look at certain drug interactions of Synthroid.
Antacids
Antacids are used to ease symptoms of conditions such as heartburn and indigestion.
Interaction result: Taking Synthroid with an antacid could make Synthroid less effective than usual.
Interaction explained: Antacids can bind to Synthroid in your digestive tract and block your body from absorbing it. This lowers the amount of medication in your system, making your treatment less effective.
Examples of antacids: Below are examples of antacids that can interact with Synthroid:
- sodium bicarbonate (Alka-Seltzer)
- calcium carbonate (Tums)
- aluminum hydroxide/magnesium hydroxide (Maalox)
Steps you or your doctor may take: Be sure to take Synthroid at least 4 hours before or 4 hours after taking an antacid. This should help prevent the antacid from attaching to Synthroid in your body, allowing Synthroid to be effective for treating your condition.
Certain oral birth control
Oral birth control is medication taken by mouth to help prevent pregnancy. Synthroid may interact with oral birth control that contains a hormone called estrogen.
Interaction result: Taking Synthroid with birth control that contains estrogen could make Synthroid less effective than usual.
Interaction explained: Synthroid is a synthetic version of a certain thyroid hormone found naturally in the body. Taking oral birth control that contains estrogen increases the level of a specific protein in your blood that binds to thyroid hormone. This causes more of the drug to get locked up in your bloodstream, leaving less active thyroid hormone available for your body to use. While it doesn’t change how Synthroid is absorbed in your gut, it means you may need a higher dose of it.
Examples of oral birth control drugs: Here are examples of oral birth control drugs that may interact with Synthroid:
- ethinyl estradiol/norethindrone (Aranelle, Gildagia, others)
- ethinyl estradiol/norgestimate (Estarylla, Sprintec, others)
Steps you or your doctor may take: Before starting Synthroid, tell your doctor if you take oral birth control. They’ll help determine whether it contains estrogen. If it does, they may prescribe a higher dosage of Synthroid than usual.
Orlistat
Orlistat (Alli, Xenical) is a medication used for weight loss.
Interaction result: Taking Synthroid with orlistat could make Synthroid less effective than usual.
Interaction explained: Synthroid is a synthetic version of a certain thyroid hormone found naturally in the body. When taken together, orlistat may attach to Synthroid and prevent the body from absorbing Synthroid. This lowers the level of Synthroid in your body, which prevents it from working as well as it usually does.
Steps you or your doctor may take: Before starting Synthroid treatment, be sure to tell your doctor if you’re taking orlistat. They can advise you on whether it’s safe to take these medications together.
If your doctor prescribes Synthroid with orlistat, you’ll take orlistat at least 4 hours before or 4 hours after taking Synthroid. This should help prevent orlistat from attaching to Synthroid in your body, allowing it to effectively treat your condition.
Synthroid may have other interactions, such as with supplements, foods, vaccines, or even lab tests. Keep in mind that the following information does not include all other possible interactions with Synthroid.
Synthroid interactions with supplements
Before you start treatment with Synthroid, tell your doctor and pharmacist which herbs, vitamins, and supplements you take. Discussing this information with them may help you avoid possible interactions.
Synthroid and herbs
There have not been specific reports of herbs interacting with Synthroid. However, it’s still important to check with your doctor or pharmacist before taking any of these products during Synthroid treatment.
Synthroid interactions with vitamins and minerals
Biotin supplements may cause inaccurate thyroid hormone test results. In turn, inaccurate test results can make it difficult for your doctor to monitor how well Synthroid is working for you.
Biotin is a vitamin that’s used for various health conditions, including improving hair, skin, and nail health. If you take a supplement that contains biotin, it’s important to tell your doctor. They’ll typically ask you to stop taking this supplement at least 2 days before they run any lab tests.
In addition, Synthroid may interact with iron and calcium supplements. If either supplement is taken with Synthroid, it could decrease the level of the drug in your body. This may make Synthroid less effective than usual.
Due to this risk, you should not take iron or calcium supplements at least 4 hours before or 4 hours after taking Synthroid. This should help prevent iron or calcium from affecting the level of Synthroid in your body, allowing it to effectively treat your condition.
Before taking any vitamins during Synthroid treatment, talk with your doctor or pharmacist. This includes multivitamins, which can also contain minerals that Synthroid may interact with.
Synthroid interactions with food
Certain foods and drinks can decrease the level of Synthroid in your body, making it less effective than usual. For this reason, it’s best to take Synthroid on an empty stomach. You’ll take the drug at least 30 minutes to 1 hour before your first meal of the day.
Examples of foods and drinks that could make Synthroid less effective include:
- grapefruit and grapefruit juice
- soy-based flour, such as that used in infant formula
- cottonseed flour
- walnuts
- dietary fiber
- coffee
- foods or drinks that contain calcium,* such as milk and other dairy products
If you have questions about foods or drinks to avoid with Synthroid, talk with your doctor or pharmacist.
* To learn more, see “Synthroid interactions with supplements” above.
Synthroid and vaccines
Vaccines and Synthroid have not been reported to interact with each other. For more information about getting certain vaccines while you take Synthroid, talk with your doctor or pharmacist.
Synthroid interactions with lab tests
Synthroid can alter the results of lab tests that measure thyroid hormone levels, especially those that evaluate protein-binding. And taking certain vitamins like biotin can cause inaccurate or false results on the blood tests your doctor uses to monitor your Synthroid treatment.
Synthroid interaction with cannabis or CBD Cannabis (marijuana) and cannabis products, such as cannabidiol (CBD), have been specifically reported to interact with Synthroid. The effects of cannabis on Synthroid can vary depending on the exact cannabis product used. Certain cannabis products may decrease the level of Synthroid in the body, which could cause Synthroid to be less effective than usual. Other cannabis products may raise the level of Synthroid in the body, which could increase your risk of side effects from Synthroid. Before starting Synthroid treatment, tell your doctor and pharmacist if you use cannabis. By sharing this information with them, you may help prevent possible interactions. Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
Certain medical conditions and other factors may increase the risk of interactions with Synthroid. Before starting this medication, be sure to talk with your doctor about your health history. Synthroid may not be the right treatment option for you if you have certain medical conditions or other factors affecting your health.
Health conditions or factors that might interact with Synthroid include:
Diabetes: Before starting Synthroid treatment, tell your doctor if you have diabetes. Synthroid can make it harder to manage your blood sugar level. For this reason, your doctor may have you check your blood sugar more often than usual while taking Synthroid. If you’re taking diabetes medication, they may adjust the dosage to help manage your blood sugar.
Heart problems: Before taking Synthroid, tell your doctor if you have heart problems, such as coronary artery disease. Synthroid may cause heart problems such as arrhythmia or heart attack as a side effect, which could worsen any heart problems you already have. To decrease your risk of heart problems, your doctor may prescribe a lower dosage of Synthroid than usual.
Being age 65 years or older: Synthroid may cause heart problems such as arrhythmia and heart attack. Your risk of these side effects may be higher if you’re age 65 years or older. To reduce this risk, doctors may prescribe a lower dosage of Synthroid for people in this age range.
Untreated adrenal insufficiency: If you have adrenal insufficiency that’s not being treated, doctors typically will not prescribe Synthroid for you. For details, see the “When to avoid Synthroid” section.
Pregnancy: Doctors typically consider Synthroid safe to take during pregnancy.
Breastfeeding: Synthroid passes into breast milk. However, it’s not known if the drug causes side effects in a breastfed child. Talk with your doctor if you’re breastfeeding or planning to while taking Synthroid.
Allergic reaction: If you’ve had an allergic reaction to Synthroid or any of its ingredients, your doctor will likely not prescribe it for you, as it could cause another allergic reaction. They can suggest other treatments that may be better choices for you.
Post-menopause: Synthroid may cause low bone density (weakened bones) as a side effect. This risk may be highest in people who have gone through menopause. If you’re post-menopausal, tell your doctor before starting Synthroid. They may order occasional bone density tests for you. If you’re found to have low bone density, your doctor may adjust your dosage of Synthroid.
Synthroid is not known to interact with these supplements.
Ashwagandha is used to ease symptoms of various health conditions, including arthritis, stress, and anxiety. Collagen supplements are used to improve skin and joint health. Turmeric may be used to reduce inflammation, ease pain, and improve digestion.
To learn more about Synthroid and these supplements, talk with your doctor or pharmacist. They can advise you on whether it’s safe to take any of them during Synthroid treatment.
No, Synthroid does not directly interact with B vitamins such as biotin and vitamin B12. However, biotin supplements may cause inaccurate thyroid hormone test results. This includes tests for thyroid-stimulating hormone (TSH) and thyroxine (T4).
If you take a biotin supplement, be sure to tell your doctor. They’ll likely ask you to stop taking this supplement at least 2 days before they run any thyroid hormone tests.
Yes, it’s believed that Synthroid is safe to take with diphenhydramine (Benadryl), an antihistamine used to treat conditions such as seasonal allergies. Synthroid and Benadryl are not known to interact with each other.
If you’re interested in an allergy treatment while taking Synthroid, talk with your doctor or pharmacist.
You can take certain steps to help prevent interactions with Synthroid. Your doctor and pharmacist are key resources, so reach out to them before starting treatment. For example, you should plan the following:
- Let them know if you take cannabis.
- Tell them about any other medications you take, as well as any supplements, herbs, and vitamins.
- Create a medication list , which your doctor and pharmacist can help you fill out.
It’s also important to read the Synthroid label and other
If Synthroid doesn’t come with paperwork, you can ask your pharmacist to print a copy. If you need help reading or understanding this information, ask your doctor or pharmacist.
You can also help prevent interactions with Synthroid by taking it exactly as your doctor prescribes.
Synthroid (levothyroxine) is a widely prescribed hormone replacement therapy for hypothyroidism, but getting your dosage exactly right requires navigating a complex web of interactions. This medication is highly sensitive. Common substances like coffee, antacids, calcium, and iron supplements can significantly impair how your body absorbs Synthroid.
Additionally, certain health conditions (such as untreated adrenal insufficiency) and medications like estrogen-containing birth control can drastically alter how the drug functions in your system. To ensure Synthroid works effectively and safely, it’s best taken on an empty stomach, spaced apart from other medications, and managed in close consultation with your healthcare professional.
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