Published on:

Calcium For Chickens: How to Prevent a Deficiency

Do chickens need calcium? They sure do! Calcium is necessary for the formation of eggs, as well as keeping your hens happy and healthy. The good news is that you do not have to do too much extra to ensure your chickens do not become deficient in calcium. Here is everything you need to know about calcium for chickens, including the roles of calcium, signs of a calcium deficiency, and how to supplement calcium into your flock’s diet.

chicken or hens walking in a farm, brown and white color

Why Do Chickens Need Calcium?

Most living creatures need a decent amount of calcium to function. For chickens, calcium is even more important. An eggshell is primarily composed of calcium carbonate, which makes up about 94% of the shell’s dry weight. The remaining 6% is made up of other minerals such as magnesium, phosphorus, and potassium. Therefore, it can be said that almost the entire eggshell is made up of calcium. Hens lay eggs every 26-48 hours, depending on the breed. If you expect that to continue, your feathered friends are going to need plenty of calcium.

Aside from using calcium for the formation of eggshells, the mineral has other essential functions within the body, including:

  • Controlling muscle spasms, particularly those needed for laying eggs
  • Maintaining the nervous system
  • Assisting with blood clotting
  • Trigger reproductive hormone production
  • Bone growth and development
  • Helps maintain a balanced pH level
  • Required for the absorption and use of phosphorus
  • Necessary for activating digestive enzymes

As you can see, the need for calcium is sufficient enough that your flock’s diet of chicken feed alone may not be enough.

The Science Behind Your Flock’s Need For Calcium

While knowing why calcium is important, it also helps to know the role that calcium plays and how a chicken’s body utilizes the mineral.

calcium chloride flakes

Calcium For Forming Eggshells

In humans, up to 99 percent of calcium is stored in our bones and teeth. It’s a bit different for your flock. Calcium is stored in a place called the medullary cavity of the bones. When needed, a single is sent out telling the medullary cavity to dump some calcium into the bloodstream. The kidneys are also commanded to stop producing excess calcium.

Once the process begins, the ovaries start releasing estrogen, signaling to the body that more calcium has be stored after what was released. This cycle happens on the regular basis, ensuring that the hen has enough calcium to lay an egg.

Calcium, Phosphorus, and Vitamin D

The eggshell is primarily composed of calcium carbonate, which makes up about 94% of the shell’s dry weight. The remaining 6% is made up of other minerals such as magnesium, phosphorus, and potassium. Therefore, it can be said that almost the entire eggshell is made up of calcium. Interestingly, your chicken needs to have a balance of all three in order for vitamin D, phosphorus, and calcium to play their roles successfully.

Phosphorus is a mineral that is essential for a variety of biological processes in chickens, including the growth and maintenance of bones and teeth, the production of energy, and the metabolism of other nutrients. It’s also important for the proper functioning of the nervous system and the regulation of pH levels in the body.

In chickens, a deficiency of phosphorus can lead to a variety of health problems, including skeletal deformities, decreased egg production, and reduced immune function. However, too much phosphorus can also be harmful, as it can interfere with the absorption of other minerals such as calcium and lead to mineral imbalances.

Vitamin D, on the other hand, is key in calcium and phosphorus metabolism. Without enough vitamin D, your chicken will not be able to absorb or use dietary phosphorus and calcium, which can result in health issues, like weakened bones and eggshells.

In addition to its role in mineral metabolism, vitamin D also has other important functions in the body, such as supporting immune function and maintaining healthy skin and feathers. A deficiency of vitamin D in chickens can lead to a range of health problems, including rickets, poor growth, and decreased egg production.

How to Spot Calcium Deficiency in Chickens


Calcium deficiencies happen when a chicken cannot or will not consume enough calcium to meet its dietary needs. That being said, calcium deficiencies may also happen when a chicken is not consuming enough vitamin D or phosphorus. Other factors, such as environment, health, age, and diet play a role in your chicken’s health.

Here are some signs of a calcium deficiency:

  • Weak, thin, or soft-shelled eggs or eggshells with bumps or deformities.
  • Reduced egg production or poor egg laying.
  • Lethargy, weakness, or reluctance to move or stand.
  • Leg and bone problems such as deformities, fractures, or weakness.
  • Muscle spasms, tremors, or seizures.
  • Poor feather quality, including thin or brittle feathers or feather loss.
  • Increased susceptibility to disease and infections.

If you notice any of these symptoms in your chickens, it’s important to address their calcium deficiency as soon as possible to prevent further health complications. Consult with a veterinarian or poultry expert for advice on how to properly diagnose and treat a calcium deficiency in your chickens.

What About a Excess of Calcium?

A deficiency in calcium is much more common in chickens, but there is also a possibility that your flock is getting too much supplemental calcium in their diet. You may think this would not be a problem, but too much of a good thing often becomes a terrible thing.

If your chickens are receiving too much calcium, they could develop a condition called hypercalcemia, which is when the overabundance of calcium in the body negatively impacts the heart, liver, and kidneys. In fact, too much calcium is toxic to kidneys. Furthermore, a chicken’s kidneys may begin to calcify.

How to Prevent Calcium Deficiency in Chickens

You are probably wondering, “Isn’t the complete layer feed that I give my chickens enough? Why do they still need supplemental calcium?” Younger hens that are laying eggs continuously are going to need more minerals than what is in the layer feed, as this allows your hen to instinctively adjust her calcium intake as she needs it. Age, diet, the weather, disease, and digestive health all play a role in how well your chicken is absorbing calcium and how much she needs to form up and lay an egg.

This is why supplemental calcium is such a benefit to your flock.

Common Methods of Supplementing Calcium for Chickens

oyster shell

Here are some methods of supplementing calcium for chickens:

  • Provide access to oyster shell or crushed eggshells: Oyster shell and crushed eggshells are both excellent sources of calcium. Crushed eggshells can be collected from your own chickens or purchased from a feed store, while oyster shells can be purchased at most feed stores.
  • Add calcium supplements to their feed: Calcium supplements can be added to a chicken’s feed in the form of calcium carbonate, which is commonly found in limestone, or dicalcium phosphate. Be sure to follow the manufacturer’s instructions for dosage.
  • Feed them calcium-rich foods: Foods that are high in calcium include leafy greens, such as kale and spinach, as well as broccoli and cabbage. Feeding your chickens a varied diet that includes these calcium-rich foods can help supplement their calcium intake.
  • Provide access to bone meal: Bone meal is made from ground-up bones and is a good source of calcium for chickens. However, it is important to make sure that the bone meal you provide is from a reputable source and is free from contaminants.

Should You Supplement Phosphorus and Vitamin D, Too?

Being that phosphorus, vitamin D, and calcium are closely linked, you may assume that you need to supplement these, as well. Fortunately, most high quality chicken feed has the correct amount of phosphorus and vitamin D for your flock to thrive. Yet, if you find that your chickens’ calcium intake needs a boost, it may means that phosphorus and vitamin D are low too.

You can offer the following to ensure every component of health has been covered:

  • Eggs
  • Broccoli
  • Meat
  • Sprouted sunflower seeds
  • Black soldier fly grubs

You may also consider letting your chickens free-range once in a while, as this gives them an opportunity to find food that fills in nutritional gaps.

Final Thoughts on Calcium for Chickens

Now you know just how important calcium is to chickens. Without an adequate amount of calcium, your hens will lay eggs with brittle shells, and they may even start to grow weak and weary. By providing supplemental sources of calcium, you can prevent a deficiency in calcium and keep your flock productive.