This is education, not medical advice. Nothing here is a diagnosis or a promise about your fertility. With nutrients, taking more can create its own problems, so treat every marker below as something to discuss with your provider, not as a shopping list.
Your body draws on nutrients to mature an egg, ovulate properly and prepare the lining for implantation. A "normal" nutrition panel can under-read your status for three reasons. Standard panels look only for outright deficiency. The marker that matters for fertility is often not measured at all (ferritin instead of hemoglobin, for example). And your body uses up its stores before a routine test shows anything. The nutrients most often under-read for fertility are iron (ferritin, not only hemoglobin), vitamin D, folate with B12, and omega-3 fats.
In my work, nutrient gaps are the factor missed most often, and luckily they are also among the easiest to put right. "Everything looks fine" is frequently true of the panel that was run. Meanwhile, the marker that matters for fertility was never checked, or it was read against the wrong cut-off. Below are the nutrients worth a closer look, along with an honest summary of the evidence for each.
Iron: the tank that empties before anemia shows
You can be low in iron without being anemic. Your body uses up its iron stores first, and only much later does the shortage show up in a hemoglobin or anemia test. Ferritin measures those stores, and it can be low while a standard "iron" check still looks normal. That is why ferritin is the number that matters for fertility.
Low ferritin has been linked to unexplained infertility. In a 2023 case-control study, ferritin below 30 µg/L showed up in a third of women with unexplained infertility and in about one in ten women without fertility problems. In the large Nurses' Health Study II, women who took iron supplements had a clearly lower risk of ovulatory infertility than those who didn't (relative risk of about 0.60). Labs often flag deficiency only below about 15 µg/L, while many clinicians treat symptoms below about 30. You will also see higher "functional" ferritin targets online. Those reflect the preferences of individual practitioners and are not an established fertility number.
No guideline sets an ideal ferritin level for conception, and iron is one nutrient you should never take in high doses without testing, because too much carries its own risks. The sensible approach is simple. Ask for a ferritin test, not just hemoglobin, and if the result is genuinely low, correct it with your provider instead of guessing.
Vitamin D: strong in one setting, mixed in another
Vitamin D behaves more like a hormone than a vitamin, and reproductive tissue is full of vitamin D receptors, so it deserves a place here. The evidence splits into two camps, though. In assisted reproduction, a meta-analysis found that women with sufficient vitamin D were more likely to have a live birth than women who were deficient. For natural conception in healthy women, the picture is mixed, and several studies found no significant difference.
Correcting a genuine vitamin D deficiency carries little risk and is good for your health in general, and the fertility findings are at least encouraging. I won't tell you that extra vitamin D will get you pregnant, though, because the research on natural conception doesn't support that. Test it, correct a real deficiency and keep your expectations realistic.
Folate and B12: beyond the neural tube minimum
Almost everyone knows folate prevents neural tube defects. Fewer women know it has also been linked to conceiving in the first place. In studies following women before conception, those with the lowest folate intake from food who took no supplement had the lowest chance of conceiving each cycle, while women at or above the recommended 400 µg a day did better. Among women having fertility treatment, higher doses of folic acid (above about 800 µg a day) and a higher B12 intake were each linked to a greater chance of a live birth. B12 works hand in hand with folate, so it makes sense to look at the two together.
Much of the strongest live-birth data comes from women having assisted reproduction, and high folate and B12 levels tend to go with a nutrient-rich diet overall, which makes cause and effect hard to separate. The practical, low-risk takeaway is that a prenatal supplement with folate before conception is standard and sensible. Folic acid is the form public health guidance recommends and the form the research used. If you carry one of the common MTHFR variants, there is no established need to switch to methylfolate. The aim is to close a gap and support your baseline. High doses won't buy you a better result.
Omega-3: promising, not proven
Omega-3 fats are building blocks for the cell membranes and signaling molecules that reproductive cells depend on, so there is a real biological reason to pay attention to them. The human studies are encouraging without being conclusive. In one group of women trying to conceive, those taking an omega-3 supplement had roughly 50% higher odds of conceiving in any given cycle than women who didn't (a fecundability ratio of about 1.51). A large North American study also linked higher omega-3 intake to a better chance of conceiving.
The findings aren't consistent. A comparable Danish study found no link, and a study that measured omega fatty acids in the blood found no difference between women who conceived quickly and women who didn't. So omega-3 is reasonable, low-risk and possibly helpful. It isn't proven. It belongs in the picture, but I wouldn't oversell it.
CoQ10 and egg quality: the mitochondria question
At the level of the cell, egg quality is largely a question of energy. A maturing egg runs on its mitochondria, and those become less efficient with age. CoQ10 (ubiquinol) plays a central role in how mitochondria produce energy and also works as an antioxidant, which explains why it is one of the most discussed fertility supplements. In a randomized trial of younger women with diminished ovarian reserve going through IVF, taking CoQ10 beforehand improved how the ovaries responded and produced more high-quality embryos.
First, that trial, like most CoQ10 research, looked at assisted reproduction and at women with reduced ovarian reserve or older eggs, not at the general population trying to conceive naturally. Second, even in that trial, pregnancy and live-birth rates improved somewhat without reaching statistical significance. CoQ10 carries little risk and makes biological sense, particularly with age or a low reserve, but the evidence stops short of proof. Discuss it with your provider rather than assuming it will work.
The trace minerals behind your thyroid
This is where nutrients start to explain what happens with your hormones. Two trace minerals do a great deal of work for your thyroid. Iron is part of the structure of thyroid peroxidase, the enzyme that makes thyroid hormone, so low iron can reduce thyroid output and slow the conversion of the storage hormone (T4) into its active form (T3). Selenium drives that same conversion, and low selenium has been linked to signs of thyroid autoimmunity. Iodine, meanwhile, is the raw material the thyroid uses to make its hormones in the first place.
I'm not suggesting you add three more supplements. The point is that a "normal" nutrient panel and a slightly off thyroid result can be two views of the same problem. This is what I mean by reading results across the whole body, and it is why no single number ever gives the full answer.
So what should I actually do with all this?
Please don't clear out the supplement aisle. Measure the right things first, then look at the results together. You could ask your provider:
"Could we check ferritin, and not only hemoglobin, along with vitamin D, B12 and folate, and then look at the results together instead of one at a time? Where something is genuinely low, I'd like to correct it properly, and where it's fine, I don't want to chase it."
That sums up the whole approach. You swap guesswork and random supplements for a clear picture of what your body actually has to work with, and you correct only what is short. I can't guarantee an outcome, and none of this replaces your doctor. It does give you something concrete to act on when you've been told everything looks fine.