Conditions Guide · Pill4Me Chilliwack
Hypothyroidism
An underactive thyroid is one of the most common conditions in Canada — affecting roughly 1 in 10 adults, and up to 1 in 5 women over 60. This guide covers levothyroxine (Synthroid), the standard treatment, including dosing, timing, interactions, and BC PharmaCare coverage.
What is hypothyroidism?
The thyroid gland, located at the base of your neck, produces hormones (T3 and T4) that regulate metabolism, energy production, heart rate, and body temperature. When the thyroid doesn’t produce enough hormone, the entire body slows down.
The most common cause is Hashimoto’s thyroiditis — an autoimmune condition where the immune system attacks thyroid tissue. Other causes include previous thyroid surgery, radioactive iodine treatment, or certain medications.
Diagnosis is made by measuring TSH (thyroid-stimulating hormone) in a blood test. A high TSH means the pituitary is working overtime to stimulate an underperforming thyroid. Treatment with levothyroxine brings TSH back to the normal range.
Common symptoms
Many of these symptoms overlap with other conditions — a TSH blood test is the definitive diagnostic step.
Levothyroxine (Synthroid)
Synthetic T4 — the standard first-line treatment for hypothyroidism worldwide.
Levothyroxine
Synthroid, Eltroxin (generics available)
How it works
Levothyroxine is synthetic thyroxine (T4) — identical to the hormone your thyroid produces. After absorption, it is converted in tissues to the active form (T3). Replacing deficient T4 normalizes metabolism, restores energy, and relieves hypothyroid symptoms.
Dosing
- Once daily — on an empty stomach, 30–60 min before breakfast
- Available in doses from 25 mcg to 200 mcg
- Dosage individualized by TSH — small adjustments are common
- Follow-up TSH check 6–8 weeks after any dose change
BC PharmaCare coverage
Levothyroxine is covered by Fair PharmaCare and Plan C. Because it is a narrow therapeutic index drug, brand-name Synthroid may be covered where clinically appropriate — discuss with your prescriber. Switching between generic and brand at refill is not recommended without a TSH recheck.
Narrow therapeutic index — consistency matters
Levothyroxine has a very narrow therapeutic window. Even small changes in the amount absorbed can shift your TSH outside the target range. For this reason, most guidelines recommend staying on the same brand or generic formulation consistently. If your pharmacy switches your formulation at refill, tell your pharmacist and request a TSH follow-up.
Important interactions & timing
Many common substances interfere with levothyroxine absorption. Timing and separation are critical.
Calcium supplements
Separate by ≥4 hours — calcium significantly reduces absorption
Iron supplements / multivitamins with iron
Separate by ≥4 hours
Antacids (calcium carbonate, aluminum, magnesium)
Separate by ≥4 hours
Coffee / espresso
Separate by ≥30 min (ideally 60 min)
Proton pump inhibitors (omeprazole, pantoprazole)
May reduce absorption — monitor TSH
Warfarin (blood thinner)
Thyroid changes affect INR — monitor closely
Cholestyramine / colestipol
Separate by ≥4–6 hours — major absorption interaction
This is not a complete interaction list. Always inform your Pill4Me pharmacist of every medication, supplement, and herbal product you take.
Frequently asked questions
Does BC PharmaCare cover Synthroid (levothyroxine)?
Yes. Levothyroxine is listed on the BC PharmaCare drug benefit plans including Fair PharmaCare and Plan C (Income Assistance). Because levothyroxine has a narrow therapeutic index, PharmaCare allows brand-name Synthroid to be covered in cases where the prescriber has indicated brand necessary — consult your pharmacist and physician about whether this applies to you. If you are switched between brands or formulations, your TSH should be rechecked after 6–8 weeks.
Why does it matter which brand of levothyroxine I take?
Levothyroxine is a narrow therapeutic index (NTI) drug — meaning the difference between an effective dose and one that causes toxicity or under-treatment is very small. While generic levothyroxine must be within 80–125% of the brand's bioavailability, the actual difference for any given batch can affect your TSH levels. Most thyroid specialists and endocrinologists recommend staying on the same brand or formulation consistently, rather than switching between brand and generic at refill.
When should I take levothyroxine?
Levothyroxine is best taken on an empty stomach — ideally 30–60 minutes before breakfast or 3–4 hours after eating. Many foods, supplements, and medications interfere with its absorption. Calcium, iron, antacids, and coffee consumed within 4 hours of levothyroxine can significantly reduce how much is absorbed. Take it consistently at the same time each day for stable thyroid levels.
How long does it take for levothyroxine to work?
It takes several weeks for levothyroxine to reach a stable concentration in your body. Symptoms of hypothyroidism (fatigue, cold intolerance, weight changes) typically improve over 4–6 weeks of treatment. A follow-up TSH blood test is usually done 6–8 weeks after starting or changing a dose to confirm you are in the target range. Your dose may need adjustment more than once before the optimal level is found.
Can I take levothyroxine with other medications?
Levothyroxine has many important drug interactions. Calcium supplements, iron, antacids (especially calcium carbonate, aluminum hydroxide), cholestyramine, and PPIs can all reduce absorption — separate these by at least 4 hours. Warfarin, digoxin, insulin, and some antidepressants can also be affected. Always inform your Pill4Me pharmacist of every medication and supplement you take.
Get consistent levothyroxine refills — delivered
Transfer your Synthroid or levothyroxine prescription to Pill4Me. We dispense the same formulation at every refill. Free same-day delivery in Chilliwack.
This page is for general informational purposes only and does not constitute medical or pharmaceutical advice. TSH targets, treatment thresholds, and BC PharmaCare coverage criteria are subject to change. Levothyroxine dosing is highly individual — consult your pharmacist or physician before starting, stopping, or adjusting any thyroid medication.