Last updated March 2026

Zinc

Fireblood uses zinc bisglycinate, a chelated form with 43% higher absorption than zinc gluconate. Each serving delivers 11 mg of elemental zinc, covering 100% of the male RDA, to support immune function, testosterone production, and over 300 enzymatic reactions in the body.

What zinc does

Zinc is a cofactor for more than 300 enzymes involved in metabolism, digestion, nerve function, and dozens of other processes. Unlike fat-soluble vitamins, your body has no dedicated zinc storage system. If you are not getting it daily, levels drop fast. An estimated 2 billion people worldwide are zinc deficient (Wessells & Brown, 2012, PLOS ONE).

On the immune side, zinc is essential for the development and function of neutrophils and natural killer cells. A 2017 meta-analysis in the journal Open Forum Infectious Diseases found that zinc lozenges reduced cold duration by an average of 33% when taken within 24 hours of symptom onset.

For men specifically, zinc plays a direct role in testosterone production. A 1996 study in Nutrition (Prasad et al.) showed that dietary zinc restriction in young men decreased serum testosterone by 75% over 20 weeks. Zinc supplementation in marginally deficient men raised testosterone levels significantly.

Why the form matters

Zinc supplements come in several forms, and absorption rates vary dramatically:

• Zinc oxide is the cheapest form. It has roughly 5% absorption. A 50 mg zinc oxide tablet might deliver 2.5 mg of actual usable zinc. Most budget multivitamins use this.
• Zinc gluconate absorbs better than oxide but can cause nausea at higher doses.
• Zinc picolinate has good absorption but limited research compared to glycinate forms.
• Zinc bisglycinate (what Fireblood uses) is zinc chelated with two glycine molecules. A study in the Journal of Nutritional Science (2014) found that zinc bisglycinate had 43% higher absorption than zinc gluconate. It is also gentler on the stomach because the glycine buffer reduces GI irritation.

Signs you might not be getting enough

• Frequent colds or infections that linger
• Slow wound healing (cuts, scratches take longer than expected)
• Reduced sense of taste or smell
• Thinning hair or hair loss
• Low energy or difficulty concentrating
• White spots on fingernails
• Skin issues (acne, dry skin, slow-healing blemishes)

Athletes and people who sweat heavily are at higher risk because zinc is lost through sweat. Vegetarians and vegans are also at higher risk because plant-based zinc sources contain phytates that inhibit absorption.

How much you actually need

The RDA is 11 mg for adult men and 8 mg for adult women. The tolerable upper limit is 40 mg per day. Going above this consistently can interfere with copper absorption, which is why Fireblood also includes copper.

Fireblood provides exactly 11 mg, matching the male RDA. Combined with a normal diet that includes some meat, nuts, or legumes, this brings most people into a solid range without the risk of over-supplementation.

The zinc-copper ratio matters. High zinc intake without copper can cause copper depletion. Fireblood includes copper bisglycinate alongside zinc specifically to prevent this imbalance.

What Fireblood includes

11 mg of elemental zinc from zinc bisglycinate. That covers the full male RDA in a single serving, paired with copper to keep mineral balance in check. The bisglycinate form absorbs well and won’t upset your stomach.

Fireblood includes zinc alongside 38 other ingredients, all with doses listed on the label. See the full formula.

See the full formula