Dietary supplements, including vitamins, minerals and probiotics, have become an essential part of many people’s daily wellness regimen. However, not all supplements are created equal when it comes to storage requirements. While most can be safely kept at room temperature, certain types are particularly sensitive to heat, light, and humidity, and must be refrigerated to maintain their potency, effectiveness, and safety. Improper storage can lead to degradation, loss of efficacy, or even spoilage, turning what should be a beneficial addition to your routine into a waste of money — or worse, a potential health risk.

According to EatingWell, the first rule is to read labels to see what the manufacturer recommends in terms of storage. Here are five supplements that experts recommend keeping in the fridge:

• Fish oil. Fish oil and other omega-3 supplements, such as krill oil and cod liver oil, are rich in unsaturated fatty acids, which are highly prone to oxidation. Exposure to heat and light can cause these oils to become rancid, producing unpleasant odors and potentially harmful compounds. Store liquid oils in a tightly sealed, opaque container in the refrigerator immediately after opening. Carefully check expiration dates, as rancid oils should never be consumed.

• Probiotics. Live microorganisms, often referred to as “good bacteria,” probiotic supplements help maintain a healthy balance in the gut microbiome. The viability of these organisms is what gives probiotics their health benefits, and exposure to excessive heat, light, or moisture can dramatically reduce their number and effectiveness. Check the label: Some shelf-stable probiotic supplements exist, but many require refrigeration after opening, or at all times.

• Liquid iron. If you’ve been prescribed an iron supplement to treat low iron levels, it may come in liquid form. Jamie Adams, a registered dietitian, tells EatingWell that liquid vitamins, like liquid iron, should be stored in the refrigerator to protect their freshness and slow the oxidative process that reduces their effectiveness.

• Flaxseed oil. Flaxseed oil supplements can spoil quickly if not refrigerated. Refrigeration also makes the omega-3 rich oil taste better.

• Vitamin C. Storing vitamin C products in the refrigerator is generally recommended to help maintain their freshness and efficacy. The cooler temperature helps slow down the oxidation process, which can degrade vitamin C and reduce its effectiveness. Refrigeration can also help prevent changes in color, texture, or smell that can occur as vitamin C oxidizes. While refrigeration is not necessary, it preserves the integrity of the supplement.

If in doubt about how to store a particular supplement, refer to the manufacturer’s website or contact their customer support for clarification. When purchasing online or from a store, choose reputable suppliers who store and transport their products properly.