How Long Can Soy Formula Sit Out? (Safety & Nutritional Concerns)

Just like all other baby formulas, prepared infant soy formula can get spoiled if left out at room temperature for more than 2 hours. If not consumed within the first 2 hours, it must be stored in the refrigerator immediately and used within 24 hours. Throw out any leftover formula in the bottle to minimize bacterial growth from the combination of the baby’s saliva and the infant formula. Shelf-stable soy milk can sit on the counter until you open it up. After opening it, you should store the milk in the refrigerator, while refrigerated soy milk requires refrigeration at all times. Shelf-stable soy milk can last a few months past the printed date, while refrigerated soy milk stays only for a few weeks. Once you open a carton or a bottle, you should finish it within 5 to 10 days, no matter the type.

Soy formulas are derived from soy protein and can be used as a substitute for breast and cow milk-based baby formulas. Intended for babies under one year old, these products account for 12% of the formula market. 

A soy protein-based formula is widely used because some parents believe it can help relieve gas and even colic.

Still, experts warn that parents shouldn’t be too quick to switch to soy formula over breast or cow’s milk unless it is medically advised.

Soy formula vs. soy milk 

Soy formula and soy milk are entirely different products. Soy formula is made of soy protein and other ingredients designed to meet an infant’s nutritional needs.

On the other hand, soy milk is made of soybeans and filtered water and does not contain the necessary nutrients to meet an infant’s dietary needs.

It should never be used as a substitute for breast milk or formula for babies younger than one-year-old.

For toddlers, soy milk is sometimes used as an alternative source of milk. But whole milk is recommended when they’re between 12 and 23 months old because it contains the fat they need to grow.

Soy milk does not have the equivalent amount of fat per serving as whole cow’s milk.

It’s important to note that if you give your toddler reduced-fat milk, such as soy milk, make up for that missed fat in other parts of your child’s diet. 

Types of soy formula 

If your pediatrician thinks soy formula is necessary for your little one, rest assured that these products are just as good as other formulas and are readily available wherever baby formulas are sold.

All baby formula brands are regulated by the FDA and must meet strict nutrition and safety standards.

Soy baby formula options in the market include: 

  • Gerber Good Start Soy 
  • Similac Soy Isomil 
  • Enfamil ProSobee 
  • Parents Choice Soy 
  • Earth’s Best Organic Soy Infant Formula 

Use quickly or store safely 

A container of powdered soy formula was left open for some time.
  1. Prepared infant soy formula can spoil if left out at room temperature.
  2. Use prepared infant soy formula within 2 hours of preparation and one hour from when feeding begins.
  3. If you do not start to use the prepared soy formula within 2 hours, immediately store the bottle in the refrigerator and use it within 24 hours.
  4. Throw out any infant soy formula left in the bottle after feeding your baby, and clean and sanitize it before its subsequent use. The combination of the baby’s saliva and soy formula can cause bacterial growth.
  5. Do not store unopened soy formula cans in vehicles, garages, or outdoors; keep them in a cool, dry, indoor place.
  6. Once a container of powdered soy formula is opened, store it in a cool, dry place with the lid tightly closed. It would be best to keep any opened liquid formula in the refrigerator.
  7. Most powdered infant formulas need to be used within one month of opening the container. Check the label and write the opening date on the lid of the container to help you remember. 
  8. Never use any formula after the use-by-date on the container.

Why and when is soy formula used? 

The soy-based formula can be an optimal feeding choice for some infants.

While it hasn’t been proven to help with fussiness or eczema, babies with certain health conditions may benefit from the soy-based formula when breast milk is unavailable by circumstance or choice. 

Soy formula may be a good choice for those infants with the following:

  • Galactosemia. A condition in which an infant is unable to break down the sugar galactose.
  • Primary lactase deficiency is a rare hereditary condition in which a baby is born without the enzyme lactase required to digest the sugar lactase.
  • Secondary lactase deficiency. This temporary lactose intolerance is usually caused by an infection that affects the gastrointestinal tract.
  • The child comes from a family who is vegan or vegetarian.

When to avoid soy formula?

Soy formula is not recommended unless the baby has a rare health condition or the family is strictly vegan or vegetarian.

If you stop breastfeeding before your baby is 12 months old or need to supplement, it is best to start with cow milk-based formula rather than soy formula unless there’s a good reason to start the baby on soy formula.

Avoid soy baby formula for:

  • Colic or fussiness since the switch will likely not be helpful.
  • A cow’s milk protein allergy because many infants who have a cow’s milk allergy are also allergic to soy protein and would benefit more from drinking an extensively hydrolyzed protein formula instead.
  • A high risk for food allergies since soy is among the most common allergens.
  • Premature babies. Soy formula can lead to decreased bone mineralization even when babies are on supplement calcium.


Is soy formula safe?

Despite some concerns about them, soy baby formulas are approved by the FDA as they contain the required nutrition for infants.

But, the phytoestrogens found in soy may have estrogen activity in the human body. As a result, experts have raised concerns about their potential to affect sexual development and immune and thyroid functions. 

Some research has also found a link between heavy menstrual bleeding and soy formula feeding in infancy.

Other research also suggests that menstruating women fed soy formula as infants may be more likely to experience more painful periods and suffer altered vaginal cell DNA.

Soy protein formula also contains a higher protein level than breast and cow milk-based formula.

This exposure is not a problem for full-term infants but may lead to reduced bone mineralization in preterm babies, especially those with impaired renal failure.

At the same time, soy plant compounds may protect against heart disease and certain cancers. 


You’ll quickly get the hang of how much your baby eats, decreasing or even eliminating the amount of formula that ends up down the drain. 

We can’t promise you’ll never dose off after you’ve prepared a bottle, but like all things, you’ve got this and will soon get the hang of things.

But always remember, “when in doubt, dump it out” is the best rule of thumb regarding baby formula.

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Hello, I am Emelda from Nairobi, Kenya. They simply call me mama Lilly. A fun of long road trips and a very good cook, along with my mommy duties to a super active girl. She inspires and challenges me in equal measure, and that is how I get to share with you our journey of triumph as we grow and tag you along.

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