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Heat's Effect on Supplements in the Mail -- Woman receiving a package

Answer:

Many vitamins and other supplements can degrade faster and lose effectiveness when exposed to excessive heat, light, oxygen in the air, or humidity. Even under ideal conditions, vitamins normally degrade over time, but this process is accelerated by poor storage conditions.

Heat can also increase the breakdown of softgel shells, which may lead to exposure of the contained ingredients to air, speeding degradation due to oxidation. Gelatin softgels can melt at a temperature of over 140 degrees Fahrenheit.

Although overly degraded supplements may not be unsafe to take, you won't receive the amount of ingredient stated on the label and may not get the desired effect.

Which Supplements Are Affected By Environmental Factors?

Here's how different types of supplements are affected by the environment, particularly heat:

Vitamins

Vitamins A, B-12, and C are inherently less stable than other vitamins such as niacinamide and vitamin E esters so be very careful to keep them out of heat (AESGP, 2003).

Also try to limit the exposure of water-soluble vitamins such as vitamin C and the B vitamins to humidity, as they are more susceptible to breakdown with moisture than fat-soluble vitamins like A, D and K. In fact, researchers have found that a high-humidity environment can cause some products to completely lose vitamin C content within a week (Hiatt, J Agric. Food Chem 2010).

Fish/Marine Oils and Seed Oils (Omega-3 and Omega-6 Fatty Acids)

The biggest risk with these oils is not heat, but exposure to oxygen in air, which can cause the oils to become rancid due to oxidation. This occurs faster, however, as the temperature increases. Many oils are packaged in ways that reduce exposure to oxygen (such as replacing air in bottled oils with nitrogen), retarding spoilage until the container is opened. Some also have added antioxidants, such as vitamin E. Nevertheless, ConsumerLab.com has found a small percentage of oil products to be rancid (see the results in the Fish Oil Review and Seed Oils Review). It is difficult to determine if this spoilage occurred before the oil was packaged as a supplement or after it was packaged. ConsumerLab.com tests all oil supplements for freshness.

Probiotics

These organisms are generally very sensitive to heat. They are also sensitive to humidity, which can cause otherwise dormant organisms to become active and then die if nutrients are not available. ConsumerLab.com has found many probiotic supplements to contain fewer organisms than listed.

Minerals

Minerals and trace elements are relatively stable in heat.

Glucosamine/Chondroitin

Glucosamine and chondroitin are also fairly stable in heat.

Herbal Extracts

These contain many different compounds with varying degrees of stability. It's best to follow general care suggestions below.

Other Supplements

Ubiquinol is naturally produced in the body, so it can withstand temperatures in the high 90s Fahrenheit. Exposure to higher temperatures will hasten degradation, but the process takes time. For example, an experiment with CoQ10 (a compound similar to ubiquinol) found a loss of only 15% after two months of being exposed to a temperature of 131 Fahrenheit. However, the addition of antioxidants, such as ascorbic acid (vitamin C), could minimize the loss to less than 5% (Kommuru, Chem Pharm Bull, 1999). Ubiquinol and CoQ10 products generally include antioxidant ingredients.

Creatine is susceptible to breakdown by moisture. In fact, in 2010 ConsumerLab.com found a degraded form of creatine (known as creatinine) in two liquid supplements, each of which provided relatively little, actual creatine. SAMe is also susceptible to breakdown by moisture. ConsumerLab.com has found problems with many SAMe products over the years -- although not those with better packaging and formulation. Alpha-lipoic acid is also highly susceptible to degradation (particularly if mixed with certain compounds like thiamin, as ConsumerLab.com reported in 2007).

Most manufacturers are aware of stability issues and add extra ingredient (an "overage") when making products so they will still provide 100% of the listed amount by the "Best By" date. They will also add information to the label advising you how to store the products to reach that date in good shape -- so take storage recommendations seriously. Some supplement ingredients are also susceptible to damage from light (particularly vitamins A, D and K). For protection, these will typically be packaged in bottles that are not transparent such as plastic or amber-colored glass.

Placing supplements in the refrigerator is not recommended (unless your home is very warm) because each time you open the supplement container, moisture is introduced and may condense. (There are two exceptions to this: Some supplements, like probiotics, liquid vitamins or fish oil may require refrigeration and this should be stated on the label. The other exception is if your supplement is in a sealed container that you plan on storing and not opening for a period of time. Once opened, it should be stored in a dry place, at room temperature.)

Signs of Heat Exposure

Signs that your supplement has been affected by heat or humidity include droplets of condensation in the bottle, liquid at the bottom of an otherwise dry the container, or brown spots and discoloration on tablets. (Purdue University News, 2010; Hiatt, J Agric. Food Chem 2010). Degraded B vitamins tend to have a sulfur smell, and degraded vitamin D can smell fishy.

What You Should Do:

  • Store supplements in their original container to prevent exposure to excessive light and UV rays. If a desiccant (drying) packet was included, keep it in the bottle.
  • Store supplements in a place that is dry and cool (ideally no higher than 73°F); Do not store in the bathroom or warm areas of the kitchen.
  • Only use refrigeration for supplements that require it on the label, or for storage of sealed containers.
  • Do not leave supplements in your car; take what you need with you and leave the rest at home. The temperature inside your car can quickly exceed even the warmest outdoor temperature.
  • If you order supplements by mail, try not to order during excessively hot periods. If you are ordering particularly sensitive products, like some probiotics, ask the merchant to send the products "cold" (with a cold pack intended to last the trip) or with overnight shipping to minimize heat exposure.

Risk of Cold Temperature?

Supplement ingredients are generally not negatively affected by cold or freezing temperatures. In fact, this can slow their decomposition and extend their shelf life. However, freezing capsules or softgels is not recommended, as it may cause them to crack.

There is a risk that opening a refrigerated bottle in room temperature may allow condensation to form the the bottle, and this moisture can accelerate decomposition. So, it would be best to allow cold containers to first reach room temperature before opening or to quickly remove what you need from a cold container and immediately refrigerate.

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45 Comments

liveto94
July 20, 2025

I cant find a company who will deliver the Curcumin I use to send it with ice/ cold packs. Most of what I have read about curcumin is to expect degradation if ordering in the heat. I normally do order in cool months but I upped my dose considerably and am about to run out. Those delivery trucks get up to 150F degrees. And just a few hours of that kind of heat can degrade this supplement. But how much degradation I don't know. I can't find the answer.

ConsumerLab.com
July 24, 2025

Curcumin is fairly stable even in very warm/hot temperatures in the 150-160 degree range Fahrenheit, according to laboratory studies. Cold shipment should not be necessary even in summer. https://pmc.ncbi.nlm.nih.gov/articles/PMC6049596/

liveto94
July 29, 2025

A huge thank you!!!!

ConsumerLab.com
July 30, 2025

Glad to help!

Sean22385
March 29, 2025

If a plastic supplement bottle arrives and it looks like it has been sucked in a bit, like from a vacuum effect. Do you think maybe it was exposed to high heat, the seal broke and let hot air out, then sealed and the vacuum effect pulled the bottle in when it cooled? Have had several plastic bottled supplements arrive like this over time.
Even had packages arrive warm indicating to me, the delivery trucks are not running A/C and are overheated by the sun. Which may happen in regular bulk transport to sellers from manufacturers and distributors too.

ConsumerLab.com
March 31, 2025

It's possible that slightly imploded bottles were subject to low pressure (such as during air transport in an unpressurized compartment). Changes in air pressure would not typically affect the quality of supplements.

Brian20027
July 16, 2024

I simply as a rule decline to order in the summertime.

Chris426
August 25, 2023

What can one do if they want to use a 7 day pill case to prevent any exposure to oxygen/heat/etc.?

ConsumerLab.com
August 27, 2023

Since pills would only be in the case for a relatively short day (days), it is not likely to be a problem as long as the pill box is kept away from high heat and humidity. If very hot and humid, you might consider placing the pill case in the refrigerator.

Nick424
August 03, 2023

Left a bottle of vitamin D supplements on the counter for a few days, no sunlight, open air exposure. Okay or toss?

ConsumerLab.com
August 03, 2023

It's probably fine to use, so long as it was at room temperature and the pills seem unchanged.

Ben422
July 18, 2023

So, if a supplement bought in a store has been in a hot warehouse and/or shipped in an unair-conditioned truck, it may suffer even more heat exposure than a supplement ordered online. There isn't any way to know except for the signs of heat exposure noted in the article.

ConsumerLab.com
July 24, 2023

You are right, and this is why ConsumerLab focuses on testing products that we select and purchase off of store shelves, as any consumer would, as opposed to other testing programs that may receive products directly from manufacturer.

NANCY418
November 16, 2021

Healthy Origins Vitamin K2. See previous post. Oil covered gel caps are Lot #190682 EXP 12/2021. Stuck together gel caps are LOT 210531 EXP 08/2023

NANCY419
November 16, 2021

Here is gist of previous post: Healthy Origins ordered in October, 2021 from amazon arrived with gel caps covered on oil. Ordered directly from Healthy Origins in November 2021, gel caps were stuck together in bottle. Signs of heat damage at amazon and Healthy Origins storage? How degraded are these vitamins? I have ordered this brand in the past and had no trouble with oiliness or being stuck together upon arrival or at home. Maybe time to retest? I have no financial interests in this product or its competitors.

Carlos413
June 25, 2021

I live in the Philippines where the temperature is usually 30 degrees C and humidity is 70. What is the best place to store vitamins B, C, E and D and other supplements?

ConsumerLab.com
June 25, 2021

It depends on what the conditions are in your home. If those are the conditions at home, consider storing supplements in a refrigerator and not leaving bottles open or out too long.

Carlos415
June 26, 2021

Thank you.

Glenn411
June 17, 2020

I try to not buy online any supplements or foods during the hot months of summer. But with prescriptions, it irks me that most health insurance plans require patients to get prescriptions by mail and then severely limit the amount that can be kept at home. This means that many of us are receiving heat-damaged prescriptions in warm weather because of health-insurance directives or requirements. What really gets me is when the patient is taking a drug that can't really be abused, such as thyroid medication, and yet the 90-day limitation and inability to refill until down to about 10 pills or fewer means we cannot control for heat damage in shipments. And if you actually have a life and are going to be on travel or have something unexpected come up, that at-home prescription limitation practically ties you down to waiting for the mail.

Diana412
July 18, 2023

COMPLAIN to your insurance/Rx benefit company! This is only going to get worse, they need to be made aware of the problem.

Valerie409
June 17, 2020

Last summer I bought several bottles of vegan omega-3 oil supplements by mail order. Each bottle arrived with the tablets melted together into a big lump, with the vegan fish oil leaking out and smelling rancid. It was completely unusable -- a waste of about $30 for each ruined bottle. So now I stock up on supplements (and chocolate chips :) ) in the spring, before the weather heats up, so that I won't need to order them again until autumn.

Arthur410
April 17, 2022

Good info, we have to do the same otherwise it gets expensive paying overnight shipping because heat is so damaging to certain supplements like fish oil & others. Any soft gel vitamins & also multiple vitamins that contain any B- Vitamins are also affected.

Glenn407
September 18, 2019

I'm confused. In the above write-up, CL states to only refrigerate if the label indicates to do so, and yet in its write-up for fish oil capsules, it seems to recommend refrigerating the fish oil capsules (and especially liquid).

We just started taking fish oil capsules and are storing them in the refrigerator to prevent rancidity. If the label doesn't state that refrigeration is needed for our fish oil capsules, should we ignore the CL suggestion in its Keep It Fresh section of the fish oil review to "If possible, refrigeration can help prolong freshness..."?

ConsumerLab.com
September 18, 2019

Refrigeration may not be necessary with fish oil softgels (which are protected from oxygen) but it can prolong shelf-life and may also reduce fishy burps. So, no downside, and some potential upside, to refrigerating fish oil softgels. Definitely refrigerate bottled fish oil.

Deborah404
September 15, 2019

My astaxanthin arrived on a hot day and spent several hours outside before I could retrieve it. Is it safe to consume or should I return it and ask for it to be re-shipped with a cold pack?

ConsumerLab.com
September 17, 2019

Hi Deborah - Like most compounds, when exposed to oxygen and heat, astaxanthin can degrade over time. However, the effect of heat is minimized when oxygen is minimized, such as in a softgel -- which is how most astaxanthin is sold -- which keeps it pretty stable. Unless the softgels were melted, the product is probably not compromised (see the ConsumerTips section of the Astaxanthin Supplements Review https://www.consumerlab.com/reviews/astaxanthin-supplements-review/astaxanthin/#storage).

Deborah406
September 17, 2019

Thank you!

Stephen400
April 26, 2018

If a desiccant pack was not included in the bottle, is it safe to add one?

ConsumerLab.com
April 26, 2018

Hi Stephen - Yes, it should be safe to add one.

Stephen402
April 26, 2018

Thank you!

ConsumerLab.com
April 26, 2018

You're welcome Stephen!

Roy399
March 25, 2018

I get most of my Rx drugs and supplements by mail, but never during hot months or winter freezes. I keep out only what I need, then store the rest in double-sealed plastic bags with desiccant packs at 40F in my fridge. To avoid condensation I always bring them back to room temp before opening a sealed bag.
..
I’m hoping to extend their life beyond the use-by-date. I commented on this back in 2016.
..
The desiccant I’m using for this is: Stack-On Safe 'N Dry Spad-60 packets by DESICCARE, INC. These are a combination silica jell & activated charcoal desiccant pack, and are available as 10 packs for about $12 by ordering them from Wal-Mart.
..
I’m also putting these in my dry hot cereals and beans to protect from yeast or mold.

Beverly397
July 19, 2017

I have been in the practice of buying locally during the summer months to avoid exposure of supplements to heat while being shipped to my home. Today when I spoke with a local vitamin store retailer(in central North Carolina) about their "ship-to-store" option, he said those products were shipped the same as they are to your home, running the same risk of heat exposure. Then I asked if their store inventory products were protected from heat during shipment. He said they used to be via refrigerated trucks, but were no longer. So, my shopping locally is now not much of a guarantee of whether what I buy has been exposed to heat. I guess I'll have to get more organized to buy enough of a supply in the weather friendly months to get through the extreme hot/cold seasons.

Robert398
July 02, 2018

My son works at Whole Foods Market and he said most of their stuff including supplements is delivered by refrigerated truck.

Richard391
June 02, 2017

"If you order supplements by mail, try not to order during excessively hot periods."

Could you provide some guidelines for what you consider "excessively hot"?

ConsumerLab.com
June 02, 2017

90 degrees Farenheit and above.

Robert393
June 28, 2018

I received a bottle of probiotics at 3 PM today. It had been on the UPS truck all day and felt warm. I inserted my kitchen instant read thermometer through the paper safety seal and got a reading of 90.5 F degrees. No surprise I guess because it's summer and outside temperatures are in the high 90's.

ConsumerLab.com
June 29, 2018

Hi Robert - Thank you for sharing this. Where did you purchase the probiotic from, and, did they offer the option of sending it refrigerated?

Robert395
July 02, 2018

Amazon said requesting a cold pack wasn't an option. They offered to overnight another bottle via UPS to see if it would arrive at a lower temp. I received it at 10:45 am and it was at 85.5 degrees, so 5 degrees cooler. Nature's Way assured me the product would still be good if it reached 90 degrees for a time because the capsules are oversupplied, but suggested I now keep it in the fridge to prevent further compromise. The bottle says to store at 75 degrees or cooler, or refrigerate.

Daniel388
July 10, 2016

Supplements and prescription medicines are often packed with a desiccant. Once the bottle is opened, is there any benefit leaving it in the bottle until the pills are finished?

ConsumerLab.com
July 11, 2016

Hi Daniel - Yes, as noted in the answer, if a desiccant packet was included, keep it in the bottle.

Roy384
May 29, 2016

Considering the high cost of both Supplements and Prescription drugs obtaining the longest possible shelf life is very important.
...
Years ago, I learned that our Federal Government stockpiles vast quantities of Rx drugs in caves, and that they undertook a project of determining if the use-by-date could be extended--and exactly how. Unfortunately they never shared their findings with the American people.
...
They have the resources and ability to test the actual effectiveness of drugs after long storage; I do not.
..
However, based on what it likely or logically true, I've started storing my supplements and Rx drugs under refrigeration at 40F in a sealed quart jar with a combination silica jell & activated charcoal desiccant pack inside it. I was able to obtain 10 packs for about $12 by ordering them from Wal-Mart. The Stack-On Safe 'N Dry Spad-60 packets have a color changing indicator, and can be recharged by heating at 200F in an oven for 6 hours. They're made by DESICCARE, INC.
...
I may eventually to into freezer at 0F.
...
I'd appreciate your comments about this.

Smitty

ConsumerLab.com
June 01, 2016

Dear Smitty - What you are currently doing may be more than you need to, but would not seem to do any harm. When you remove the container, let it get back to room temperature before opening, or you may get condensation inside the container. Storing at below freezing could potentially be a problem, as it could affect the chemical structure of products.

Helen386
March 28, 2018

It would seem wise to store unopened and rarely used products in the refrigerator and then keep them at room temperature when using. I live overseas part of the time, and I keep several boxes in the vegetables compartment untouched for months. Should I also close them in a plastic bag?

ConsumerLab.com
March 28, 2018

Hi Helen - While it could not hurt to put them in a bag, there is little humidity in a refrigerator to be concerned about.

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