Diclegis: what it treats, how to take it, side effects
Last updated September 3, 2026.
Diclegis combines doxylamine (an antihistamine) with pyridoxine (vitamin B6) in a delayed-release tablet, and it is the only FDA-approved prescription drug specifically for nausea and vomiting of pregnancy. It is for morning sickness that diet and lifestyle changes have not controlled, and its safety record in pregnancy is among the most studied of any drug.
What does it treat?
Nausea and vomiting of pregnancy in women who do not respond to conservative management, which means the small-frequent-meals, ginger, and trigger-avoidance basics came first. The combination is also available over the counter in its components (doxylamine sleep aids plus B6), but the prescription version is a studied, delayed-release formulation with the dosing schedule worked out.
How do you take it?
On an empty stomach with a glass of water, swallowed whole, on a titration schedule: 2 tablets at bedtime on day 1; if symptoms persist into day 2 afternoon, add a morning tablet on day 3; if still not controlled, add a mid-afternoon tablet on day 4, up to 4 tablets daily maximum. It is taken daily, not as-needed, and the need is reassessed as the pregnancy progresses, since morning sickness typically fades after the first trimester. Missed dose: take it when remembered unless the next is near; never double up.
Side effects to know
- Common: drowsiness, by far the most frequent; the bedtime loading of the schedule exists partly to sleep through it.
- Serious: the anticholinergic cautions apply to the doxylamine half: worsening of narrow-angle glaucoma, urinary retention, and asthma or breathing problems all belong on the prescriber's list, and alcohol and other sedating drugs stack with the drowsiness. No driving until you know your response.
Who should not take it?
It is intended only for pregnant women, and within that group the cautions are glaucoma, bladder-neck obstruction, stomach blockage, and concurrent sedatives or MAO inhibitors. Severe, unrelenting vomiting with weight loss and dehydration is not morning sickness anymore; it is hyperemesis gravidarum, and that needs medical care, not a tablet schedule.
When is it an emergency?
Call 911 for trouble breathing or severe allergic reaction. Inability to keep any fluids down for 24 hours, dizziness on standing, dark or scanty urine, or racing heartbeat means dehydration and needs same-day care. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Is it actually safe for the baby?
It is among the most-studied drugs in pregnancy. The doxylamine-pyridoxine combination has decades of use and large cohort data behind it, and it holds FDA approval specifically for pregnancy nausea, a bar almost nothing else in obstetrics clears. Nothing in medicine is zero-risk, but this is as close to a settled answer as pregnancy medication gets.
Why does the dose build up over days?
Because the goal is the lowest dose that controls symptoms. Two bedtime tablets cover many women; the schedule adds a morning dose, then an afternoon one, only if nausea keeps breaking through. It tops out at 4 tablets a day. Stair-stepping beats starting high and discovering you never needed it.
Why on an empty stomach?
Food delays the delayed-release tablet's absorption and blunts the timing the schedule is built around, especially the bedtime dose that needs to be working by morning. Take it with water, at least an hour before or two hours after eating.
Can I just take Unisom and B6 from the drugstore?
The components are the same drugs, and many clinicians openly suggest that route for cost reasons, with exact dosing guidance. The prescription product adds the delayed-release formulation and a worked-out titration schedule. Do not improvise doses on your own; either route should run through your obstetric clinician.
Will the drowsiness go away?
It is worst in the first days at each dose level and usually settles as you adjust, and the bedtime-heavy schedule parks most of it in your sleep. If daytime doses make you unsafe to drive or function, that dose is too high for you, and stepping back is the answer.
When do I stop taking it?
As pregnancy progresses and symptoms fade, typically after the first trimester, the need is reassessed and the dose tapered down. Some women with persistent nausea continue longer under supervision. It is a symptom-driven drug, not a fixed course.