If you started iron tablets and then stopped going, those two things are connected. Constipation is the first side effect the NHS lists for iron tablets, and iron supplements also turn up inside the NHS advice for preventing constipation in pregnancy, which is an odd place to find a pill you were told to take.
Here is what makes this different from every other pregnancy complaint with a list attached to it. Every other line on that list is something you can go and do this afternoon. That one is not yours to act on alone, and most of this post is about how to hand it to somebody who can.
Everyone hands you a list. One line on it is not yours to cross off.
My three-year-old and I talk about poop more than we talk about anything else. There is a chart on the back of the bathroom door, there is a small person who announces her results to the room like a weather report, and there is a mother who stands in that same bathroom twenty minutes later doing arithmetic she does not say out loud.
That is the shape of it. You become the household authority on somebody else’s digestion while your own goes quiet, and the quiet is embarrassing in a way that is hard to explain, because it is the least serious thing happening to your body and it is the thing you think about most. Being pregnant with a toddler already means running your own symptoms in the background of somebody else’s day, and this is one more thing that goes in the background.
So you look it up, and you get a list. Fiber, exercise, water, iron supplements. Four bullets at the same rank in the same box, and only one of them is a subtraction.
The wording on that fourth one is careful in a way the first three are not. It tells you to ask your doctor whether you can manage without them or change to a different type. It does not tell you to stop. That is a sentence written for two people to read together, and you have been handed one half of it.
There is a version of this waiting on the other side of the birth as well, with its own dread and its own week of avoidance, and I am not going to pretend it is unrelated. The first bowel movement after birth is the sequel to this, and it is worth reading before you need it rather than during.
What you are allowed to change on your own
Before this pregnancy I would have told you I ate plenty of fiber. Then I actually counted a day, on the back of an envelope, out of curiosity rather than diligence, and the number was far enough off that I counted it again in case I had missed a meal.
Here is the full set the NHS puts on its list for preventing constipation in pregnancy, all four:
- Eat foods high in fiber, such as whole grain breads and cereals, fruit and vegetables, and beans and lentils
- Exercise regularly to keep your muscles toned
- Drink plenty of water
- Avoid iron supplements, which can make you constipated, and ask your doctor whether you can manage without them or change to a different type
The first three you can start before lunch. The fourth is a conversation, and it is the only one on there that needs somebody else in the room.
The fiber one is worth a number, because “eat more fiber” is not an instruction, it is a mood. ACOG puts the recommendation for women at 25 grams a day and says most Americans get around 15. A ten gram gap is a bowl of something, not a personality change. That reframing did more for me than any amount of resolve, because it turned a vague failing into a shopping list.
The change that actually moved anything was smaller and stranger than all of that. I had been taking the tablet first thing on an empty stomach, because somewhere I had absorbed the idea that this was the efficient way to do it. Moving it to straight after breakfast sits inside what the NHS already advises, which is to take iron tablets with or soon after food to reduce the chance of side effects, and it took about four days before I could tell.
That is not the same as solving it. It is the difference between a bad week and a week you can work around, and I will take it.
The color, and the search that follows it at 3am
Nobody warns you about this one, and it is the one that will get you out of bed.
Iron tablets turn your stool dark. Properly dark. The first time I saw it I was pregnant with my first, it was the middle of the night, and I sat on the edge of the bath with my phone and typed the kind of search you only type when nobody is awake to see you do it. I did not mention it to anyone for two days. It had genuinely not occurred to me that the pill I was swallowing on purpose could be the explanation.
There are five side effects on the NHS list for iron tablets. Have all five in advance, so that none of them arrives as a surprise at three in the morning:
- Constipation or diarrhea
- Stomach pain
- Heartburn
- Nausea
- Darker stools than usual
Five things, four of them merely unpleasant and the fifth one frightening. That is an unkind ratio for a leaflet most people skim on the way out of a building.
Knowing the color is expected is not the same as knowing that every dark stool is the tablet, and I am not going to hand you a rule for telling those apart, because there isn’t one you can apply from your own bathroom. What I would say is that the search itself is the signal. If you are typing symptoms into a phone at night, you have already decided it is worth somebody’s attention, and the threshold for calling in pregnancy is lower than most of us behave as though it is.
The aisle where the labels do not tell you the difference
I have stood in that aisle. It is a short aisle and it takes a long time. Everything on it is the same three colors, half the boxes say gentle, and none of them explain what makes one different from the box beside it.
ACOG sorts the whole shelf into three kinds, and the sorting is more use than any box front:
- Bulk forming laxatives, which absorb water and expand, adding moisture to the stool so it is easier to pass. These are the ones ACOG describes as thought to be the safest
- Stool softeners, which add liquid content to soften the stool
- Stimulants, which use a chemical to increase bowel activity and move stool through the intestines
The caution ACOG attaches lands on the third kind. Laxatives in general and stimulants in particular are to be used with care, stopped once you are regular again, and overusing stimulants can leave your bowels depending on them. Which of these belongs in a pregnancy, if any, is not written on a box either, and now you are standing in an aisle holding two questions instead of one.
They are the same question. The line you cannot cross off by yourself has two possible endings in the NHS wording, managing without the supplement or changing to a different type, and both of them need somebody who has seen your blood count.
So here is the sentence, and it fits in a doorway on the way out of an appointment. The iron is constipating me. Can I switch to a different type, or do I need this one? You are not building a case and you are not asking permission to stop. You are asking which of the two doors in their own guidance is yours.
The answer may well be that you keep taking it, and it helps to know that before you ask. On the anemia side the NHS is blunt: it is important to keep taking the tablets, even if you get side effects. Both of those sentences come from the same organization and they do not cancel each other out. One of them is about how you feel. The other is about the reason you were put on them in the first place.
The bottle is now the most dangerous thing on the nightstand
My daughter can open things now. Not everything, but enough, and she does it with the patient two-handed concentration of someone who has all afternoon and no reason to hurry.
Iron supplement tablets are to be kept out of the reach of children, and the NHS does not soften what is behind that instruction. An overdose of iron in a young child can be fatal. That is the whole sentence and there is no version of this post where I write it more gently.
Mine had been living on the nightstand, because that is where you put the thing you have to remember every day. It had been there for weeks. I had walked past it every morning thinking about whether I had taken it and not once about whether anybody else could reach it.
Two more useful things sit on that same page. Drinking orange juice after a tablet may help your body absorb the iron. And where iron tablets are prescribed for iron deficiency anemia, the course usually runs about six months, which is longer than most people picture when they are handed the first box.
The bottle lives in a kitchen cabinet now, above the counter, behind the door that sticks. I take it after breakfast because that is when I am already standing in that room, which turns out to be the only reason any habit in this house has ever held.
All of that is mine to decide, and after everything above, that is a small relief. Where it lives, what I take it with, what time of day. The single thing I cannot decide on my own is whether it is in the house at all.
The short version
- Three of the four fixes are mine and I can start them today. The fourth is a sentence I say out loud at an appointment.
- Take it with food or straight after it rather than on an empty stomach, and give it a few days before deciding it did nothing.
- Dark stools are expected. Knowing that in advance is the whole difference between noticing and panicking.
- Ask which of the two doors applies to me, managing without or switching type. Do not decide it alone and do not quietly stop.
- Move the bottle somewhere a toddler cannot reach today, not on Saturday when there is more time.
Sources
- NHS, “Common health problems in pregnancy” (page last reviewed 22 April 2024)
- NHS, Health A to Z guidance on iron deficiency anemia (page last reviewed 26 January 2024)
- American College of Obstetricians and Gynecologists, “Problems of the Digestive System”, FAQ (last updated August 2022, last reviewed November 2025)
A note on this post. Written and edited by the NewBloom editorial team. NewBloom is not written by doctors, nurses or midwives, and nothing here is medical advice. We read the current guidance from bodies like ACOG, the CDC and the NHS and write down what it says, with every claim traced to its source and named in the sentence where it appears. General guidance is not the same as an answer about your own body. Your doctor, midwife or health visitor can examine you and we cannot, so anything here that raises a question about your own pregnancy is a reason to ask them. If something is wrong right now, contact your doctor or your local emergency number. More about how we write these posts.