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Episode 55 • March 2, 2026 

Listener Question:

Does Supplement Timing Matter?

Episode Highlights

1️⃣ Supplement timing can affect absorption, effectiveness, and even your medications.

2️⃣ Iron, calcium, vitamin D, omega-3s, B-complex, curcumin, & magnesium all have timing tips to know about.

3️⃣ Taking supplements at the right time can improve results and reduce side effects.

Resources

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PODCASTS:

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Transcript

 On today's episode of the PKD Dietitian Podcast, we have a listener question episode and the question of the day is from Andy B. who wrote in asking, does the timing of when I take a supplement affect how well it works or not? A simple question, not so much a simple answer. The short answer is yes, no, and it depends. When it comes to supplements, how, when, and what you take them with can impact both that supplement's absorption and effect, but also can potentially impact any medications you are taking, making them more or less effective.

 

Now, this episode isn't a deep dive into supplement interactions. If it was, it would be an epically long episode, but more of an overview for you. I want you to start thinking about the supplements that you are taking and how they can be impacted by timing and other components of your routine.

 

Don't worry, I'm going to hit on some really good tips on timing for some common supplements taken in the PKD world. That being said, I highly recommend that you talk with your dietitian and or medical provider and do a deep dive into what you are taking or even thinking about starting to ensure that the dose and timing are optimal for you, or even if it's a good supplement for you at all. If you have had a kidney transplant, it's a totally different ballgame when it comes to supplements because lots of them do interact with your anti-rejection meds.

 

This episode really isn't tailored for you. Also, this is not a list of supplements that I'm saying you should start or need to be taking. I very much believe in individualized supplements and goals around them.

 

 Instead of making some big, basic, and broad statements about supplement timing, I'm going to highlight seven supplements that many of my clients take or ask me about. So join me in looking at iron, curcumin, calcium, vitamin D, omega-3 fatty acids, B-complex vitamins, and magnesium. We're going to look at the timing for taking them and some potential interactions that are worth knowing about.

 

We are going to start with iron because, well, iron is the most sensitive supplement of the group. If you are taking iron or read any of the labels around iron, it often recommends to be taken on an empty stomach or one to two hours before or after eating. This is when it's best absorbed because iron likes a little acid, stomach acid, that is.

 

However, some folks don't tolerate iron on an empty stomach. For my clients who are struggling with tolerating iron, I have them try taking it before bed. If you are taking calcium, magnesium, or zinc supplements, avoid taking them with your iron supplement.

 

And on a side note, my favorite iron is called Vitron C. I find it to be very well tolerated with no constipation, and I see really good results with my clients who are iron deficient or need supplementation. When it comes to interactions that could impact your iron, I mentioned calcium, magnesium, and zinc. These three compete for absorption in your gut with iron, so they ultimately can reduce how much you are absorbing.

 

Curcumin and fiber supplements also can impact your iron absorption because they bind to that iron and they can prevent it from being absorbed up to 90%. If you are supplementing both iron and curcumin, take them separately a minimum of two to four hours apart, if not more. Next up, we have curcumin, which is the active and ingredient in turmeric.

 

When it comes to timing, curcumin likes a little fat, so take it with a meal or snack that has fat for better absorption. Black pepper also helps to increase absorption, and you'll find that many curcumin supplements on the market add a little black pepper extract just because of that so they can boost absorption. There are a few curcumin interactions to be aware of when it comes to timing.

 

Curcumin can have what is called, and I have this in parentheses, anticoagulant properties. This just means it has blood thinning properties. If you are already taking meds that are anticoagulant meds like Coumadin or Warfarin, even Eliquis, know that by adding curcumin, there is the potential to increase your blood thinning, and this increases the risk of bruising.

 

It's always a good idea to mention to your doctor who prescribes your blood thinner and follows you that you are adding curcumin or taking it, really add an abundance of sheer caution. Remember, curcumin can really impact iron absorption, so it's best to take those two supplements separately. If you are curious to know more about curcumin, what it is, and why folks in the PKD community are supplementing with it, I will link out both the blog I have and podcast episode 24 on this episode's note page.

 

 Along with all the other resources and references from today's episode. Number three, calcium. It's already been mentioned a couple times, but when it comes to timing, if you are taking a calcium supplement, never take it between meals.

 

Always take it with food. When calcium is taken in between meals, there is an increased risk for kidney stone formation. Calcium supplements do have several interactions worth knowing about.

 

If you have been diagnosed with hypothyroidism and are taking medications for it, like Synthroid, don't take a calcium supplement at the same time. It will decrease that meds absorption and potentially impact how effective it is. Take those at least four hours apart.

 

Some folks in the PKD community are on hydrochlorothiazide, better known as HCTZ, which is often prescribed for blood pressure. Know this, this medication can increase how much calcium your body holds onto. So taking a calcium supplement while also taking HCTZ could potentially lead to higher blood calcium levels.

 

And folks, you don't really want those calcium levels above normal in your blood. And of course, as it's been mentioned, do not take calcium at the same time as iron because they do compete. Supplementing with calcium, by the way, should be monitored by your dietician and your doctor.

 

It is not just something that you should add on just because. With any kidney disease, you do not want to overload on calcium supplements because they can create additional problems and concerns. I am very careful and intentional with clients if and when they need to add calcium supplementation, and it's usually a very low dose to mitigate known risks.

 

 Often connected with calcium and bones is our next vitamin to look at, vitamin D supplementation. When it comes to timing, vitamin D also likes a little fat. It is a fat-soluble vitamin, so it is best to take it with a meal to optimize that absorption.

 

I usually have clients take vitamin D with their first meal of the day, which is usually breakfast. There are a few potential interactions plus medication combos to know about when it comes to vitamin D supplementation. So when you add certain medications plus vitamin D, they can potentially lead to those high blood calcium levels I was talking about.

 

And folks, this is more of a concern with lower kidney function, but I really want to highlight why supplements need to be intentional, dose-specific, and your labs or outcomes monitored. So back to those medication and vitamin D supplement combos to be aware of. If your doctor puts you on something called calcitriol, taking this with vitamin D can lead to higher than normal blood calcium levels.

 

It's not that you have to stop, you absolutely need to be monitored. And there's a triple whammy if you are also taking hydrochlorothiazide, the HCTZ, with calcitriol and vitamin D. Taking these together is definitely the potential to make calcium levels go above normal. I have some great resources for you around vitamin D and PKD.

 

 I'm going to list them out in the show notes page. Episode 17 of this podcast is about vitamin D and PKD, how to supplement safely. And I also have a blog about the ultimate guide to vitamin D and PKD.

 

 Really good resources. Number five, let's talk a little bit about omega-3 fish oil. When it comes to timing, omega-3 is not surprising, fat soluble, and I usually recommend it with a meal.

 

Many of my clients take it with their first meal and also with vitamin D. There are some really good omega-3 supplements on the market, Nordic Naturals being one of my favorites, that don't come with that fishy burp or aftertaste. If you are sensitive to that, just pop your omega-3 in the freezer and take them frozen. Of course, make sure you don't forget to take them.

 

Some potential interactions with omega-3 fatty acids include, much like curcumin, omega-3 supplements can have that anticoagulant blood thinning effect. And if you are taking those prescription anticoagulant meds, the Coumadin, Warfarin, or Eliquis, there's the potential for omega-3 supplements to increase blood thinning. Talk with your doctor or dietician before starting one or review if you are already taking one.

 

Next up in our timing and interaction overview is a B-complex. When it comes to timing, B-complexes aren't very picky. B vitamins are water soluble.

 

It can be taken with or without food. A lot of folks take them first thing in the morning. Some potential interactions and impacts for taking them include, if you are taking a long-term B vitamin, high doses of B6 can cause, actually cause nerve toxicity over a long period of time.

 

This is somewhat rare, but look at what you're taking. You might be taking a B-complex or you also might add in other things that have B vitamins. It's always good to look at the totals.

 

B vitamins can also interfere with the outcome of some lab tests. For example, biotin, which is vitamin B7, can mess with thyroid hormone testing, so you get results that really aren't true. I always like to have my clients hold their B-complex among other things several days before taking labs.

 

And an FYI that I always tell my clients, when you take it, a lot of times it can change the color of your urine, sometimes even to a neon yellow. So it's nice to know that ahead of time so there isn't a freak out moment. Now last but not least is magnesium.

 

When it comes to magnesium, there are many different types. The two most common that I run into are magnesium glycinate and magnesium citrate. For timing, magnesium glyconate is the one that has that nice relaxing effect.

 

The best time to take it is about 30 to 60 minutes before bed to aid with that relaxation benefit. And some of my clients actually see benefits in the evening with their muscle cramping when they add it to their nighttime routine. You just have to be careful not to take it with your iron.

 

Timing is flexible with magnesium citrate. Some potential interactions and impact if you take magnesium are don't take it with zinc or calcium because they do compete for absorption. And if you are taking antibiotics or those super sensitive thyroid medication, magnesium can interfere with their absorption.

 

So don't take them together or near each other. And also note that if you start at the full dose of magnesium, especially magnesium citrate, it can put you on the toilet. So go slowly if you are magnesium citrate.

 

And that brings us to the end of our review of timing and potential interactions for seven common supplements that are taken with PKD. Thank you, Andy, for the great question. And to you, my loyal listeners of the PKD Dietitian Podcast for tuning in, I hope you are walking away with a new perspective on how to look at and ask about timing and potential interactions with supplements or even some really nice PKD pearls from today's episode.

 

Bottom line here is there can be better times to take different supplements, and it ultimately comes down to improving absorption, reducing interactions, and supporting better tolerability. I love getting these questions. It really lets me know what you are confused about or asking about within the PKD community and how I can help answer those questions.

 

So if you have a question for the PKD Dietitian, of course, which is me, please send a message to us at info at thepkddietitian.com. All the links mentioned today for episodes and additional blogs, plus additional resources to get more information around supplements you are taking or considering adding, they can all be found with the show notes at thepkddietitian.com/55. And until next time, folks, happy and healthy eating.

References