What Is Horse Capillary Strength Powder and Does It Work?

Supplements for horses are nothing new—but one product that’s grown in popularity, especially among performance horses, is capillary strength powder. Often marketed as a support for circulation, respiratory function, and bleeding prevention, this supplement is commonly added to feed in powder form.

But what exactly is capillary strength powder? And does it live up to the claims?

In this post, we’ll break down what it is, who uses it, the ingredients it typically contains, and what current research (if any) says about its effectiveness. As with any supplement, knowing what’s in it and how it may affect your horse is key—especially when it’s used to manage serious symptoms like nosebleeds or signs of stress under heavy physical exertion.

If your horse has been showing vague symptoms or behavior shifts and you’re unsure what’s going on, start by reviewing early signs of illness before turning to supplements.

What Is Capillary Strength Powder for Horses?

Capillary strength powder is a nutritional supplement designed to support vascular integrity—essentially, helping blood vessels function efficiently and resist damage under stress. It's most often used in horses that experience bleeding during intense exercise, especially in disciplines like racing or barrel racing.

These supplements are typically formulated with bioflavonoids such as hesperidin and rutin, along with vitamin C, vitamin K, and sometimes herbal ingredients like yarrow or grape seed extract. Together, these ingredients are believed to strengthen the walls of capillaries and small blood vessels, reduce inflammation, and support respiratory performance. Before adding any supplement, it’s essential to monitor your horse’s vital signs regularly to understand what’s normal. You can learn how in this guide to horse vital signs.

While the name might suggest it's solely for horses with vascular issues, many owners use it proactively—especially for performance horses under high cardiovascular strain, or those prone to exercise-induced pulmonary hemorrhage (EIPH).

What Are the Claimed Benefits?

Manufacturers and some horse owners claim that capillary strength powders can offer a range of benefits, particularly for high-performance horses or those showing early signs of respiratory stress.

Here are the most commonly promoted benefits:

Reduces nosebleeds during exercise

Some horses, especially those involved in intense cardiovascular activities, may experience bleeding from the nostrils after exertion. Capillary strength powders are marketed as helping reduce the frequency or severity of these episodes by reinforcing vessel walls.

Supports vascular and respiratory function

By promoting stronger capillaries and reducing inflammation, these powders aim to improve blood flow and oxygen delivery—both essential for horses in training, competition, or recovery.

Promotes stronger vessel walls

Bioflavonoids like hesperidin and rutin are known for their ability to support vascular health. They may help capillaries remain more elastic and less prone to rupture during high blood pressure events like sprinting or jumping.

Helps performance horses under stress

Whether it's hauling, heat, altitude, or intense physical demand, supplements like this are commonly used by riders and trainers as a preventive measure for horses under frequent stress.

Supports horses prone to exercise-induced pulmonary hemorrhage (EIPH)

EIPH is a condition in which blood enters the lungs during intense exercise. Though capillary strength powder is not a treatment for EIPH, it’s often included as part of a broader support protocol to minimize risks.

While some of these benefits are based on anecdotal feedback from riders, trainers, and grooms, it’s important to look at what the science says too—which we’ll cover in the next section. If your horse is showing signs of illness or subtle changes in behavior, it’s best to start with a full health check. This early signs of sickness guide is a great place to start.

Is It Commonly Used in Equine Care?

Yes—capillary strength powder is widely used in the performance horse world, especially in disciplines where high-speed, high-intensity work is routine. This includes:

• Racehorses

• Barrel racing horses

• Eventers

• Polo ponies

• Older horses with compromised circulation

It’s typically administered as a powder mixed into the horse’s feed once or twice daily. Some formulas are combined with additional vitamins, minerals, or joint support ingredients, depending on the product’s target purpose.

Although not as mainstream as joint supplements or electrolytes, capillary strength powders have gained traction in barns where respiratory efficiency and recovery play a big role in daily performance. Owners of older horses, or those recovering from respiratory illness, sometimes add it to support blood vessel health and general lung function.

There are several brands available on the market, each with slightly different formulas, but most share the same core ingredients: bioflavonoids, vitamin C, and sometimes herbs or antioxidants.

What Does the Research Say?

When it comes to capillary strength powder for horses, the scientific backing is limited and somewhat mixed. While many of the ingredients—especially bioflavonoids and antioxidants—are supported by human studies, research specific to equine health is still emerging. For example, this research summary on flavonoids and capillary function (PubMed) suggests improvements in vascular integrity in humans, though more equine-specific trials are needed.

Limited clinical trials in horses

At present, there are very few peer-reviewed studies that directly examine the effectiveness of capillary strength powders in horses. Most existing data is either anecdotal or extrapolated from human and small-animal studies. This makes it difficult to say definitively how effective these supplements are for preventing bleeding or improving vascular resilience in equine athletes.

Supportive findings in human and veterinary research

Bioflavonoids like hesperidin and rutin have been shown in human studies to support vascular health, reduce inflammation, and improve capillary integrity. These compounds may be beneficial in horses as well, but more equine-specific studies are needed to confirm dosage, absorption, and overall impact.

Use in EIPH management protocols

Some veterinarians may recommend capillary support supplements as part of a larger protocol for managing exercise-induced pulmonary hemorrhage (EIPH)—a condition where horses bleed from the lungs during intense exertion. However, these supplements are typically used alongside prescription medications, not as standalone treatments.

Veterinary oversight is essential

Because of the lack of regulated studies and the variation in supplement formulas, it's important to consult your veterinarian before adding capillary strength powder to your horse’s routine. Certain ingredients could interact with medications or mask symptoms of underlying conditions, making it harder to catch problems early.

Supplements should never replace veterinary care. If you suspect your horse has respiratory issues, review our post on average horse heart rate and how to check it to identify potential warning signs.

If your horse is experiencing symptoms like recurrent nosebleeds, labored breathing, or behavioral changes under stress, it’s worth addressing those concerns with your vet first—before turning to supplements.

Are There Any Risks or Side Effects?

Capillary strength powders are generally considered low risk when used appropriately, but like any supplement, they’re not without potential concerns—especially if given without veterinary guidance.

May interfere with medications

Some ingredients, particularly those that affect blood vessels or circulation, could potentially interfere with other treatments. For example, if your horse is on anti-inflammatory drugs, blood thinners, or prescription medications for EIPH, always check for compatibility before adding any supplement.

Can mask symptoms

Using capillary strength powder without identifying the root cause of bleeding, stress, or respiratory problems can delay diagnosis. If a horse improves slightly due to supplementation but continues to perform below normal, underlying health issues may go unnoticed.

Not a replacement for veterinary care

Supplements like this are designed to support, not treat. They should never replace a proper examination, diagnostics, or prescription treatment. Always consult your vet before starting your horse on any supplement—especially if the symptoms include nosebleeds, labored breathing, or signs of collapse.

Caution with certain conditions

Horses with bleeding disorders, ulcers, or those recovering from surgery may need to avoid certain ingredients. For example, citrus bioflavonoids and high-dose vitamin C could potentially irritate the stomach or increase bleeding risk in sensitive horses.

Conclusion

Capillary strength powder is a widely used supplement in the performance horse world, promoted for its ability to support vascular health, reduce bleeding episodes, and aid in respiratory resilience. While some of its ingredients are supported by research in humans and small animals, equine-specific data remains limited.

That doesn’t mean it’s without value—many riders and trainers report improvements when using it as part of a larger care routine. But as with any supplement, it should be used thoughtfully and under the guidance of your veterinarian.

If your horse is showing signs of respiratory stress, exercise-related bleeding, or discomfort during training, the first step is always to rule out medical issues. From there, capillary strength powder may have a role to play in keeping your horse performing at their best.

FAQ

Is capillary strength powder suitable for everyday horses or just performance horses?

While it’s most commonly used in racehorses and competitive athletes, some owners choose to use it for older horses or those with minor respiratory concerns. However, for non-performance horses without symptoms, there’s usually no proven benefit. Your vet can help determine if your horse would actually benefit from vascular support.

Can I give capillary support powder alongside other supplements like electrolytes or joint support?

In many cases, yes—but it depends on the product formulations. Some supplements share overlapping nutrients like vitamin C or bioflavonoids, which could lead to oversupplementation. Always review ingredient labels and consult your veterinarian to avoid potential interactions.

How long does a horse need to be on capillary support before seeing results?

Results vary widely. Some owners report improvements in a few weeks, while others see no change at all. If you don’t observe any benefit after 30 to 60 days, it’s worth re-evaluating your horse’s needs with a vet rather than continuing indefinitely.

Is capillary strength powder legal for competition horses?

Most products use naturally sourced ingredients and are generally considered legal. However, competition rules vary between organizations. If you compete under FEI, USEF, or breed-specific rules, confirm with your governing body to ensure compliance.

Can this supplement help with recovery after intense training or hauling?

Possibly. While not marketed as a recovery product, the circulatory support it offers may help horses bounce back more comfortably from stress. It should be used in addition to, not in place of, hydration, proper rest, and post-exercise care.

Does every horse with EIPH need capillary strength powder?

Not necessarily. EIPH is a serious condition that often requires veterinary management with medications and adjusted training plans. Capillary strength powder may help reduce symptoms in some horses, but it’s not a standalone solution and should only be part of a broader care plan.