Is thiamine for hyperemesis gravidarum safe during pregnancy?

What does the evidence say about thiamine for hyperemesis gravidarum during pregnancy?

1. The 2024 RCOG guideline recommends thiamine for patients admitted with vomiting or severely reduced intake, especially before dextrose or parenteral nutrition. This is a clinician-managed nutritional indication, not a reason for everyone with mild nausea to take high doses. 1
2. A systematic review identified 177 reported cases of Wernicke encephalopathy associated with hyperemesis. The cases highlighted prolonged vomiting, inadequate thiamine, and severe neurologic harm, but a collection of case reports cannot estimate the risk for all patients with hyperemesis. 2
3. A 2024 clinical review emphasizes that glucose administration during thiamine deficiency can precipitate or worsen Wernicke encephalopathy. It calls for protocols that account for thiamine before dextrose in patients with prolonged vomiting and poor intake. 3
4. MedlinePlus lists confusion, loss of coordination, and visual or eye-movement changes among signs of Wernicke encephalopathy. Hyperemesis is one possible cause of thiamine deficiency, and suspected illness warrants immediate hospital assessment. 4
5. The guideline includes oral and intravenous approaches to thiamine, chosen according to the clinical situation. Inability to retain tablets or concern about neurologic deficiency changes the management question; a standard prenatal supplement cannot be assumed sufficient. 1

Is thiamine for hyperemesis gravidarum safe in each trimester?

• First trimester. Mention the duration of vomiting and any inability to retain prenatal vitamins or food. Thiamine depletion can arise early, and a laboratory result or obvious underweight appearance is not required before a clinician considers nutritional support.
• Second trimester. Persistent restricted intake requires reassessment even when intermittent IV fluids improve dizziness. The route and amount of thiamine depend on absorption, intake, and whether neurologic symptoms are present.
• Third trimester. Vomiting that persists or returns later needs review of other causes and nutritional status. After discharge, follow the prescribed nutrition and vitamin plan and seek immediate help for new confusion, visual changes, or poor coordination.