Most foods are considered fine to eat for breakfast as long as they are eaten 30 to 60 minutes after taking levothyroxine. Levothyroxine should be taken once a day on an empty stomach in the morning.

Taking the medication on an empty stomach is recommended because it increases absorption of the drug. Also, some foods are known to lower the absorption of levothyroxine from the intestine and should be avoided at the same time as taking levothyroxine. These include:

• Soybean products
• Cottonseed meal
• Walnuts
• Dietary fiber
• Grapefruit juice

Coffee and cow's milk have also been reported to decrease the drug's absorption. How each of these foods impair levothyroxine absorption is not completely understood and may vary from person to person. The time necessary to wait before drinking cow's milk after taking levothyroxine has not been determined. Also, the effects and proper timing of other calcium-containing foods such as yogurt or plant-based milks have not been evaluated.

Hormone levels should be checked regularly.

Levothyroxine is a synthetic form of the thyroid hormone T4. It is prescribed for people who do not produce enough of their own thyroid hormone (those who have hypothyroidism). With hypothyroidism, you will require thyroid hormone replacement for your whole life.

The effectiveness of levothyroxine therapy is measured by monitoring your symptoms and by checking the amount of two main thyroid-related hormones, thyroid stimulating hormone and T4, in the blood. Levothyroxine is usually started at a low dose and slowly increased over time. The full effects of levothyroxine may take weeks to months to realize.

Medications may interact with other medications. This is called a drug-drug interaction. Sometimes medications are affected by the food you eat. When this happens, it is called a food-drug interaction. Levothyroxine is known to have both drug-drug and food-drug interactions. It may also interact with supplements you take.

For example, it is known that calcium-containing supplements decrease levothyroxine absorption, so it is hypothesized that the interaction with cow's milk is due to its calcium content. However, this has not been proven. According to the FDA label, calcium supplements should not be taken within 4 hours of taking levothyroxine.

Bottom line

Ways to minimize the effects of food interactions on levothyroxine:

• Wait a full hour before eating breakfast or drinking coffee after taking levothyroxine
• If you eat foods at breakfast that are known to affect levothyroxine absorption, eat consistent amounts each day
• Have your thyroid hormone levels checked regularly as recommended by your doctor