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The Warning Signs of Low Calcium Levels During Exercise

warning signs of low calcium

When we sweat, we lose small amounts of minerals, including sodium, potassium, calcium and magnesium. Collectively known as electrolytes, these minerals play important roles in our ability to perform physically, and to train at the top of our ability.

This blog post details the effects of calcium on our training and racing. To learn more about the impact other electrolytes have on the body, check out our earlier blogs on sodium and potassium.

What can trigger a calcium deficiency?

We get calcium from our diet, and healthy sources include low-fat dairy, salmon, sardines and dark greens like kale, broccoli, swiss chard and bok choy. However, most adults do not meet the recommended daily intake of 1,000 mg, which over time can lead to chronic deficiency. Other common reasons for low calcium levels include:

  • Vitamin D deficiency: Vitamin D helps the body absorb calcium, and low levels of Vitamin D are correlated with low calcium levels.
  • Low magnesium levels: Similarly, magnesium is crucial for calcium absorption. Even when you are getting enough calcium in your diet, if you aren’t meeting your magnesium needs, you could still suffer from low calcium levels.
  • High phosphorus intake: This usually results from a high consumption of soft drinks.
  • Surgeries, medicines or chronic medical conditions: Serious but rare instances of low calcium levels can result from invasive surgeries, abnormal thyroid hormone levels or treatments like chemotherapy.

What are the warning signs of low calcium levels?

Everyone knows calcium is important for strong bones, but this important electrolyte has a role in a wide number of physiological processes, including muscle contraction, the transmission of neural impulses and the production of certain hormones. Thus, when the body does not contain sufficient levels of calcium, these functions break down. Notable symptoms include:

Muscle cramps or weakness: Because calcium plays a role in conducting neural signals, inadequate levels can lead to uncontrolled or insufficient electrical activity—the kind that causes muscle cramps. When neural activity is diminished due to low electrolyte levels, the brain realizes its impulses are not strong enough to prompt muscular contractions, and it often doubles down to send even more powerful signals. The resulting firestorm of neural activity can inhibit muscle relaxation, causing a cramp.

Other muscular symptoms can include fatigue, weakness or even pain when moving. These sensations, most often felt in the arms and thighs, are one of the earliest signs of a calcium deficiency.

Fatigue or fainting: Due to its role in blood pressure management, low calcium levels can also lead to fatigue or weakness after standing up. Insufficient calcium levels have also been linked to insomnia, which can further contribute to feeling tired.

Brittle nails, bones and hair: When we suffer chronically low levels of calcium in the blood, the body responds by leaching the mineral away from other sources like bones, hair and fingernails, which can leave them brittle and more susceptible to breaks. This is especially bad news for athletes in high-impact sports like running, basketball or CrossFit®. Calcium is one of the building blocks of many parts of the body—most notably the skeletal system—which must be able to withstand all of the pounding that accompanies training.

In extreme situations, low calcium levels have been linked to alopecia, a reversible but traumatic condition in which hair falls out in clumps.

Itchy skin: Low calcium levels have also been linked to dry, itchy skin and in some cases, more severe conditions like eczema or psoriasis.

Low calcium and athletes

Low calcium levels can be particularly harmful to athletes looking to compete at the top of their game. To achieve physical success, we must have a strong skeletal system capable of withstanding the constant pounding that occurs during training, as well as a functioning nervous system that wards off painful cramping and fatigue.

Calcium, like all electrolytes, is lost through sweat during exercise. The exact quantity is low compared to sodium and potassium, but over time—say during the course of a long-distance triathlon—it adds up. Although the body can replace calcium in the blood by pulling it away from the bones, that process is neither desirable nor quick. In other words, unless athletes take steps to replace the calcium they lose through sweat, they are at risk for experiencing many of the unpleasant symptoms listed above.

Can low calcium levels be fixed?

If diet is the reason for your low calcium levels, the solution is to eat more mineral-rich sources like fish and dark greens. If you find that is not enough to meet the recommended daily intake of 1,000 mg, supplements can also help. Popular options tend to contain around 600 mg of calcium and 800 IU of Vitamin D to help with absorption. Provided you are eating a healthy diet, this should be sufficient to meet your daily needs.

If your low calcium levels are the result of another cause, like a chronic medical condition, it’s best to talk to your doctor directly about ways to improve calcium intake.

How to prevent low calcium levels

The easiest way to avoid low calcium levels is to ensure you are getting enough from your diet, which should be rich in dark greens, nuts and seeds.

During training and racing, you may also find it helpful to consume a supplement designed to replace calcium lost through sweat. SaltStick, for example, is uniquely designed to replace the full spectrum of electrolytes, including calcium, and in a form and quantity the body can absorb. Many of our products contain Vitamin D as well, to help with absorption (although Vitamin D is not critical for this process). As a reference, here’s how much calcium is contained in each serving of SaltStick products:

  • SaltStick Caps (1 Capsule) 22 mg of calcium
  • SaltStick Caps PLUS (1 Capsule) 14 mg of calcium
  • SaltStick Fastchews (2 Tablets) 10 mg of calcium


