When you first start taking thyroxine, some doctors may start you on the lowest possible dose. Other doctors (including Dr. Friedman) will recommend starting on a full replacement dosage unless you are elderly or have heart problems. The advantage of starting on a full replacement dose is that you will feel better sooner. The dose you take will be based on several factors, including your age, weight, the cause of your hypothyroidism, and whether you are taking other medications. A rough guide is the dose of T4 in micrograms you will need is equal to your weight in kilograms times 1.6. One kilogram equals 2.2 pounds.

In general, the more you weigh, the higher the dose. And if you are older, you will probably start on a low dose so that your body can adjust. Drugs generally move more slowly in older people, so you may wind up staying on a low dose. But if you do need more medication, your doctor will probably increase it very slowly.

The cause of your hypothyroidism also may dictate the dose you receive. If you have Hashimoto's disease or mild hypothyroidism, for instance, some doctors believe your thyroid may still be making some hormone, and you probably need a lower dose. Other doctors recommend full replacement even for mild hypothyroidism. But if you have had your thyroid removed, you will often need a higher dose to make up for the missing hormone. In any case, taking too much thyroxine can trigger symptoms of hyperthyroidism — anxiety, restlessness, and a rapid heartbeat.

Whatever thyroid hormone replacement drug you wind up taking, it's critical that you take it correctly and follow your doctor's orders closely. Becoming familiar with your thyroid hormone drug — which drugs and foods affect it, how to store it, and when to expect to feel better — can make a big difference in how well the medication works for you. Here are some important facts to know.

Be Consistent

The key to successful thyroid hormone replacement is taking it every day — every single day. One of the most important things you can do to ensure that you remember to take your pill is to take it at the same time every day. Most doctors recommend taking your pill first thing in the morning. Link it to another daily habit such as brushing your teeth or just before taking your morning shower. Some people find it easier to remember by keeping their pills in containers marked by the days of the week.

If you miss a dose, don't panic. T4 tends to remain in your blood for a long time. Simply take your pill when you remember it. If you forgot to take your pill yesterday, you can take one pill (the forgotten one) in the morning and one in the evening. It's best to not take two pills at once. Or, you can probably skip the one you missed. If you're concerned, call your doctor or pharmacist and ask what you should do.

It's also important to take the brand that you are prescribed. Although each brand contains the same active ingredients, some of the filler ingredients may differ and can affect the way your body absorbs the drug. If you do want to try another drug, you must do so under a doctor's supervision and get your TSH tested and dosage adjusted, if necessary.

People who take drugs that contain T3 should talk to their doctors about taking their drugs at different times of the day. T3 is a faster-acting drug that loses its effect after just a few hours. Taking it two or three times a day can sometimes help even out your hormone levels.

Give It Time

You've been taking your pill every day for three weeks now, but you're still feeling lousy. You may be wondering why the drug isn't working. Meanwhile, your sister noticed improvements in just two weeks. What's going on?

In reality, the impact of thyroid medication varies from one person to the next. For some people, the effects may kick in in just two weeks. In others, it might take six weeks before the drug starts to work and you notice any significant improvements. In any case, around four to six weeks, your doctor will do another set of thyroid tests. If your TSH levels are still high — or they've gone too low — your doctor will need to adjust your dosage accordingly.

In some cases, it can take months before you and your doctor pinpoint the best dosage. Be patient. Finding the best dose is a matter of trial and error. You will eventually find the right dosage.

Store It Properly

Most people stash their medications in the bathroom cabinet, where they're easily accessible in the morning or evening. But in reality, the bathroom isn't always the best place for drugs that need to be at room temperature, which includes most thyroid medications.

Levothyroxine, for instance, is sensitive to heat. Heat and steam from several showers can raise the temperature in a bathroom cabinet enough to affect the potency of the drugs stored there. Other storage places you need to beware of include kitchen cupboards near the stove or dishwasher, the glove compartment of your car, or a counter or window ledge that sits in direct sunlight.

Instead, store the drug at room temperature in cabinets that are removed from heat and light. The only drug for hypothyroidism that requires refrigeration is liotrix (Thyrolar).