Is magnesium L-threonate safe during pregnancy?

What does the evidence say about magnesium L-threonate during pregnancy?

1. The only safety assessment of magnesium L-threonate as a supplement ingredient sets a maximum intake of 3,000 mg a day, providing about 250 mg of elemental magnesium, and explicitly limits that recommendation to the general adult population, excluding pregnant and lactating women. 1
2. A randomized trial of a magnesium L-threonate supplement explicitly excluded pregnant women, breastfeeding women, and women intending to become pregnant during the study, which is typical of how this ingredient has been studied so far. 2
3. Reviewers recommending an optimal prenatal supplement point to a different amount and form: about 350 mg a day of magnesium from a well-absorbed form, while specifically advising against the poorly absorbed oxide form. 3
4. The tolerable upper limit for supplemental magnesium in adults, 350 mg a day, was set because of diarrhea at higher doses, and researchers reviewing pregnancy studies using other magnesium forms at 300 to 384 mg a day found no significant increase in digestive symptoms. 4
5. A six-week trial of magnesium L-threonate in adults found it was generally well tolerated, with mild digestive symptoms like loose stools reported at similar rates in the supplement and placebo groups, but this trial specifically did not include anyone pregnant. 2

Is magnesium L-threonate safe in each trimester?

• First trimester. No studies have tested magnesium L-threonate specifically in early pregnancy, and the ingredient's own safety review excludes anyone pregnant. If you're taking it and get a positive pregnancy test, bring it up with your provider at your first visit rather than continuing it on your own.
• Second trimester. There's still no pregnancy-specific data on magnesium L-threonate by the second trimester. General prenatal magnesium research has used other forms like citrate or glycinate at studied doses, so ask your provider whether switching forms makes sense for you.
• Third trimester. Magnesium needs don't change dramatically by the third trimester, but this ingredient still has no pregnancy safety data at any stage. If leg cramps or another concern has you considering magnesium late in pregnancy, your provider can point you to a form and dose that's actually been studied.