Synthroid (levothyroxine): What you need to know

Synthroid is a brand name for levothyroxine, the most common medicine for underactive thyroid (hypothyroidism). If your doctor prescribed it, this short guide helps you use it smarter: how to take it, what to watch for, and how to safely order it online when needed.

How to take Synthroid

Take Synthroid on an empty stomach, usually 30–60 minutes before breakfast or 3–4 hours after your last meal. That gives the best, most consistent absorption. Swallow the tablet with a full glass of water. Try to take it at the same time every day so your dose stays steady.

Avoid taking calcium, iron, antacids, or multivitamins within four hours of your dose — they bind levothyroxine and reduce how much your body absorbs. Soy products and high-fiber meals can also interfere, so keep timing in mind if you eat those often.

If you miss a dose, take it as soon as you remember that day. Don’t double up the next day to catch up.

Monitoring, side effects, and special situations

Your doctor will check blood levels (TSH, sometimes free T4) about 6–8 weeks after a dose change and then periodically. If your TSH is high, you might need a higher dose. If it’s low, your dose might be too strong.

Symptoms of too little thyroid hormone: tiredness, weight gain, cold sensitivity, slow heart rate. Too much: nervousness, fast heart rate, weight loss, trouble sleeping. If you notice these, talk to your doctor — don’t change the dose yourself.

Pregnancy usually increases your need for levothyroxine. Women who are pregnant or planning pregnancy should tell their doctor so levels can be checked more often. Some medicines — like amiodarone or certain blood thinners — can interact with levothyroxine. Always list Synthroid when reviewing your meds.

Generic levothyroxine is widely used and usually fine, but switching brands can cause small differences in absorption. If your pharmacy switches your brand, ask your doctor if repeat blood tests are needed.

Store Synthroid in a cool, dry place away from direct sunlight. Keep it in its original container to avoid moisture.

Thinking of buying Synthroid online? Make sure the pharmacy requires a prescription, shows clear contact info, and is verified by a pharmacy watchdog (look up CIPA or PharmacyChecker). Very cheap prices or no-prescription offers are red flags. Check reviews and confirm there’s a pharmacist you can contact if you have questions.

If you need help comparing online pharmacies or checking legitimacy, our site covers tips on safe online ordering and what to look for when shopping for meds from home. And remember: any dose changes should come from your prescriber after blood tests, not from an online purchase alone.