Many people experience problems when taking thyroxine. Before suspecting that the dosage is wrong, or the brand you’ve been given may be incorrect, make sure that you’re not doing anything yourself to prevent your thyroid medication from working correctly.
Be Consistent With Your Thyroid Medication
The key thing is consistency: take the same dosage at the same time, with the same interval from foods, each day. After you’ve been on the medication for a week or so, which is how long it takes to build up to optimum levels, you’ll notice your body “expecting” a dose of thyroxine at that time. If you become inconsistent with the timing, undesirable side-effects can build up.
Consistency is more important than which time of day you choose to take your medicine. Although most doctors recommend taking Synthroid or any form of Levothyroxine first thing in the morning, many people find they suffer from fewer side-effects if they take their dose mid-morning (three or four hours after breakfast), or even last thing at night. In fact, recent studies have shown that a night-time dose seems to be the most effective, least disruptive and best-tolerated time for taking thyroid medication.
Make Sure You Drink Enough Water
The majority of the thyroxine dose is absorbed from the small intestine (the jejunum and upper ileum). To “propel” the pill down to the jejunum you need to drink a full glass of water – about 300ml (half a pint). This is essential, as the drug will not be adequately absorbed from other sites in the body.
Many people on thyroid medication keep a bottle of water beside their bed so they can take the synthroid or levothyroxine tablet upon waking, with plenty of water and nothing else. This helps to give the tablet time to absorb as you go about getting up; showering, shaving, putting on make-up and so on, before you’re even tempted to eat breakfast. It is critical to allow at least one hour before eating or drinking anything else, to allow the medication to be absorbed and converted correctly in the body.
Don’t Eat or Drink Anything That Stops Thyroxine Absorption
Some substances bind with thyroxine, preventing it from crossing the gut wall to be absorbed. These substances should never be taken at the same time, or within an hour of taking thyroxine tablets:
- iron salts
- antacids
- calcium carbonate (including milk)
- sucralfate
- cholestyramine
Leave at least four hours if possible between taking calcium or iron supplements and a dose of thyroxine. Be sure to check that any orange juice you drink is not fortified with calcium, as even a small amount will affect absorption.
Be consistent with what type of foods you eat too, within reasonable limits. Eating higher-fibre foods means you’ll need a higher dose of thyroxine. If you were eating a high-fibre diet when you established the dose, stay with that diet. If you were suddenly to switch to a lower-fibre diet, your body would receive a higher dose of medication. Likewise, if you were eating lots of low-fibre foods, build more fibre into your diet very gradually, and keep your doctor informed as you may need to increase your thyroxine dose.
Many people find that cutting down on tea and coffee helps enormously, and recent research suggests plausible reasons: caffeine seems to prevent full absorption of thyroxine, while tea has a high fluoride content (see below).
Hidden Fluoride Affects the Thyroid
Flouride works wonders for our teeth, but spells disaster for those with hypothyroid conditions. Doctors actually used to treat hyperthyroid conditions (i.e. people with over-active thyroids) with fluoride – because it is so effective at slowing down the actions of this gland. Chief sources are tap water, toothpaste and tea. For this reason you may like to consider using a water purifier or filter, and buying fluoride-free toothpaste (available from many supermarkets and most health stores). Switching to herbal or fruit teas and avoiding the green and black teas will decrease your fluoride intake dramatically.
Soy Inhibits Thyroid Hormone Production
While soy is considered a healthy food on most levels, its isoflavones present a problem for anyone suffering from a hypothyroid condition. This is more pronounced in certain people; those with Hashimoto’s autoimmune thyroiditis seem particularly sensitive to soy’s thyroid-dampening effects. You can easily test its reaction on yourself by eating a soy-based product (such as soy sauce on rice or noodles); any “slowing down” effect will be felt within an hour.
The reason for this is that soy’s isoflavones inhibit the thyroid peroxidase which makes T3 and T4; people with hypothyroidism of any sort already make too few of these hormones, so soy makes a bad problem worse.
If you are taking any vitamin E supplements, check that they are not made from or using soy – most of them are, and these will act against your medication and act as a “thyroid-dampener,” like any other soy product. Either take your vitamin E at night (if you take Synthroid/Levothyroxine in the morning), or – better still – switch to a non-soy version.
Thyroxine–Drug Interractions
Be aware that Synthroid and all other forms of thyroxine may interact with other prescription drugs, possibly affecting both their efficancy and that of the thyroxine. Check with your doctor to see if you need to adjust your dosage if you are on anti-depressants: tricyclic and tetracyclic antidepressants can increase thyroxine’s toxicity. And don’t be tempted to take any form of “recreational” drugs while on thyroxine – many of them will interact to cause hypertension and tachycardia.
References
- “Soy Protein Isolate Increases Hepatic Thyroid Hormone Receptor Content” Wenxin Huang, Carla Wood, Mary R. L’Abbé, G. Sarwar Gilani, Kevin A. Cockell and Chao Wu Xiao: the American Society for Nutritional Sciences, Journal of Nutrition. 135:1631-1635, July 2005
- Effect of long-term fluoride administration on thyroid hormones level blood in rats.” Bobek S, Kahl S, Ewy Z.; Endocrinol Exp. 1976;10(4):289-95.
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