Yes — unless your doctor has specifically told you to stop or reduce one of them, iron, calcium and vitamin D are usually continued together right through the third trimester, because each one is covering a different, genuinely increasing need at this stage. Feeling fine is not, by itself, a reason to stop any of them.
Why each one matters more, not less, by 31 weeks
- Iron — your blood volume keeps expanding through the third trimester, and your baby is building their own iron stores for the months after birth, so your iron requirement actually rises rather than falls as you approach term
- Calcium — your baby's skeleton is mineralising fastest in the third trimester, and if your intake falls short, your body will draw calcium from your own bones to meet the baby's need
- Vitamin D — works alongside calcium, since your body needs adequate vitamin D to actually absorb and use the calcium you're taking; one without the other is less effective
Why they're often spaced apart through the day
- Iron and calcium compete for absorption when taken together, so many doctors prescribe them at different times of day — commonly iron in the morning (sometimes with a source of vitamin C to help absorption) and calcium, often combined with vitamin D, at night
- If you've been taking all three together and haven't had any issues, don't change the timing on your own — ask your doctor to confirm the schedule that's right for your specific prescription
- Tea, coffee and dairy taken at the same time as your iron tablet can reduce how much of it you absorb
When the plan might actually change
- If your blood counts come back well above the lower threshold your doctor is targeting, they may reduce (not necessarily stop) the iron dose
- If you're having significant gastrointestinal side effects from iron — nausea, constipation, acidity — tell your doctor rather than skipping doses on your own; there are often alternative formulations
- Vitamin D doses are sometimes adjusted based on a blood level test rather than given as a flat dose for everyone
None of these three supplements work as a "nice to have" by this stage of pregnancy — they're addressing needs that are actively increasing as you approach your due date, which is exactly why doctors are reluctant to have patients stop early.
Frequently asked
Can taking too much calcium cause problems with the placenta?
There's no good evidence that calcium taken at the doses doctors prescribe in pregnancy causes early placental calcification or similar problems. Placental changes seen on scans later in pregnancy are a normal part of placental ageing, not a result of your calcium intake.
I missed a few doses of calcium or vitamin D — does that harm the baby?
A few missed doses are not a cause for alarm. Simply resume your normal schedule — don't double up to "catch up." If you're missing doses frequently, mention it to your doctor so they can simplify the regimen if needed.
Do I need to keep taking all three even after delivery?
Often yes, at least for a period after birth, particularly if you're breastfeeding or your blood counts were on the lower side during pregnancy. Your doctor will usually review this at your postpartum visit rather than having you stop automatically at delivery.
What if I can't tolerate swallowing more tablets by this point in pregnancy?
Tell your doctor rather than stopping one on your own. There are different formulations (including liquid or chewable options for some supplements) and dosing schedules that may be easier to manage while still meeting your needs.