Skip to Content

Fergon Side Effects

Generic Name: ferrous gluconate

Note: This page contains information about the side effects of ferrous gluconate. Some of the dosage forms included on this document may not apply to the brand name Fergon.

For the Consumer

Applies to ferrous gluconate: capsules, tablets

Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Constipation; darkened or green stools; diarrhea; loss of appetite; nausea; stomach cramps, pain, or upset; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur while taking ferrous gluconate (the active ingredient contained in Fergon)

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); black, tarry stools; blood or streaks of blood in the stool; fever; severe or persistent nausea, stomach pain, or vomiting; vomit that looks like blood or coffee grounds.

For Healthcare Professionals

Applies to ferrous gluconate: compounding powder, oral capsule, oral liquid, oral tablet, oral tablet extended release


Gastrointestinal side effects are generally dose-related and have included nausea, constipation, anorexia, heartburn, vomiting and diarrhea. In addition, stools may appear darker in color in patients taking ferrous gluconate (the active ingredient contained in Fergon)

Oral preparations may rarely cause Hemoccult-positive stools, patients with positive tests generally require further work-up.[Ref]

The gluconate salt is generally less irritating to the gastrointestinal tract compared to the sulfate salt. Gastrointestinal side effects may be further minimized by initiating ferrous gluconate therapy at smaller doses and gradually titrating upwards until the desired dose is achieved.

Gastrointestinal discomfort may also be minimized by administering each dose with food. However, concurrent administration of ferrous gluconate with food may decrease the amount of iron absorbed.

The use of enteric-coated or delayed release iron preparations may reduce adverse effects because of the small amount of iron released and absorbed. Enteric-coated or delayed-release ferrous gluconate products are not recommended for use.

Constipation may be relieved by administering docusate sodium 100 mg to 200 mg per day in addition to increasing the intake of oral fluids, such as water.[Ref]


1. "Product Information. Ferrous Gluconate (ferrous gluconate)." Paddock Laboratories Inc, Minneapolis, MN.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Not all side effects for Fergon may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.