A group of European experts put together in 2025 the study in European thyroid journal the new guidelines on the use of levothyroxine in adults with hypothyroidism. They analysed hundreds of studies and concluded that almost half of patients do not achieve adequate control of thyroid-stimulating hormone, known as TSH, despite taking medication chronically. A significant part of the problem is related to everyday factors such as diet, dosing schedules and interactions with other nutrients and drugs.
These recommendations are aimed at adults with hypothyroidism who use levothyroxine on a daily basis. For them, small details in routine can make the difference between a stable TSH and persistent symptoms such as tiredness, cold, mental fog or muscle weakness. Understanding what influences drug absorption helps to make more informed decisions about diet, supplementation and daily habits.
European guidelines show that levothyroxine is effective but very sensitive to everyday life
The European Thyroid Association document summarises the available evidence on levothyroxine monotherapy, which is the standard treatment for hypothyroidism. It collects data from millions of prescriptions worldwide and reviews clinical, observational studies and uptake trials in patients with difficulties in stabilising TSH.
Experts emphasise that levothyroxine has a narrow therapeutic margin. This means that small variations in dose or absorption can result in out-of-range TSH. They also point out that many patients receive doses adjusted only by weight, without taking into account age, digestive comorbidities, concomitant drugs or dietary changes, which makes it difficult to maintain a stable situation.
Levothyroxine absorption depends on the stomach, intestine and accompanying nutrients.
Levothyroxine is absorbed mainly in the small intestine, but requires a preliminary step in the stomach. There, the tablet must be broken down in an acidic environment to make the active substance available. If the gastric pH is higher than normal, for example due to the use of proton pump inhibitors, atrophic gastritis or Helicobacter pylori infection, higher doses are usually required to achieve the same effect.
Guidelines emphasise that levothyroxine is best absorbed on an empty stomach and at least 30-60 minutes before breakfast. Some foods and supplements, particularly those containing calcium, iron or certain fibres, can physically bind to the molecule and reduce its passage into the blood. Even coffee taken too close to the pill decreases the thyroxine peak in the blood and delays its arrival at the maximum level.
Interactions with other nutrients are also described. Calcium and iron are the best known examples, but other compounds present in juices, protein powders or antacids are cited as modifying bioavailability. For this reason, the guidelines recommend careful review of supplements and concomitant medication when TSH does not stabilise despite apparently adequate doses.
Daily habits recommended by the guidelines for more stable levothyroxine therapy
The first pillar stressed by the experts is regularity of intake. Choosing a fixed schedule, for example one hour before breakfast or at bedtime at least three hours after dinner, helps to reduce TSH fluctuations. The important thing is to maintain this pattern over time and not to alternate chaotically between morning and evening.
The second aspect is to separate levothyroxine from other supplements and drugs that may interfere. Guidelines advise at least a four-hour buffer with calcium- or iron-containing products, as well as with certain bile acid chelators and some antacids. In practice, this usually means taking levothyroxine alone and shifting other tablets to another time of day.
A third point is to monitor digestive status. Problems such as coeliac disease, lactose intolerance, inflammatory bowel disease or bariatric surgery may increase the need for levothyroxine. In these cases, the guidelines recommend a specific assessment, as the cause is often not the pill itself, but the intestine’s ability to absorb it.
Finally, the authors insist on not changing brand or formulation without control. If for any reason the preparation is changed, they advise repeating TSH and free thyroxine after six weeks. This is to check whether the new presentation maintains the previous balance or whether adjustments are needed.
How Nutribiolite MAG-FUSION fits into a routine consistent with levothyroxine guidelines
The European levothyroxine guidelines devote a specific section to nutritional factors that may influence treatment. These include minerals that interact with the intestinal absorption of thyroid hormone. Magnesium is included in this group because it shares transport pathways and can form complexes with levothyroxine in the gastrointestinal tract when taken together.
This information is relevant to anyone considering a magnesium supplement such as MAG-FUSION as part of a daily care routine. The key message is not to avoid magnesium, but to organise your schedule better. Separating the intake of levothyroxine from any mineral supplement respects the physiology described in the guidelines and allows both thyroid treatment and magnesium to be used for other bodily functions.
Responsible use of magnesium supplementation in the context of treated hypothyroidism
People with hypothyroidism who are already taking care of their diet, physical activity and medication schedules often seek additional support for overall well-being. In this scenario, a magnesium supplement such as MAG-FUSION can be part of an orderly strategy if the temporal separation from levothyroxine is respected, following the logic of the guidelines.
The consistent approach is to consider levothyroxine as a fasting priority and reserve magnesium supplementation for another time of the day, for example with lunch or dinner. This minimises competition for intestinal absorption and keeps supplement use in line with official recommendations on nutrient interactions with thyroid medication.
MAG-FUSION is intended for adults who wish to integrate magnesium into their daily routine, while respecting the timing of their thyroid medication.
Final summary, the importance of details in the management of hypothyroidism
The European Thyroid Association guidelines remind us that levothyroxine works best when its physiology is respected, i.e. when it is administered consistently, on an empty stomach and separated from nutrients that may interfere with its absorption. Adjusting these details reduces the risk of unstable TSH and persistent symptoms.
Integrating supplements such as a magnesium product within this logic, with well-differentiated schedules, allows other aspects of wellbeing to be taken care of without detracting from the efficacy of the main treatment. In summary, the central message is to organise the daily routine around levothyroxine and build a coherent lifestyle from there.
This content is for information only and is not a substitute for the advice of a healthcare professional.
Frequently asked questions
Why are the guidelines so insistent on how to take levothyroxine?
Because levothyroxine has a narrow safety margin and its absorption changes with fasting, gastric pH and the presence of other nutrients. Taking it always at the same time, on an empty stomach and separately from food and supplements improves TSH stability.
What is the relationship between magnesium and levothyroxine according to European guidelines?
The guidelines include magnesium among the minerals that can interfere with levothyroxine absorption when taken together. They therefore recommend separating thyroid medication and mineral supplements over time to reduce interactions in the gut.
Can I use a magnesium supplement if I take levothyroxine daily?
The guidelines do not advise against magnesium, but they do recommend against taking it at the same time as levothyroxine. A practical option is to reserve the medication for the morning on an empty stomach and the magnesium for another meal of the day, following the logic of temporal separation.
What other habits help levothyroxine therapy to be more stable?
In addition to respecting fasting and separation with supplements, regularity in schedules, avoiding frequent brand changes and monitoring for digestive problems are also helpful. Guidelines advise reviewing these factors before increasing doses repeatedly.
What type of person can MAG-FUSION fit into this routine?
MAG-FUSION may be suitable for adults who have already organised their levothyroxine intake and wish to take magnesium at another time of the day. This respects the absorption of thyroid treatment and integrates the supplement into a routine consistent with official recommendations.
