Nandrolone for Horses: Dosage Chart, Calculator & Safety Guide for Owners
Written & Reviewed By: Medshorse Team
Last Updated: October 2026
A thin, run-down horse that will not rebuild condition is a worry for any owner, and nandrolone for horses is one of the injectables a vet may bring up. It is also one of the easiest drugs to get wrong, because the dose is in milligrams while the syringe is in millilitres.
Quick answer: the veterinary reference dose for nandrolone in horses is 1 mg per kg of body weight, given by deep intramuscular injection every 4 weeks. That is about 500 mg for a 500 kg horse. Only a veterinarian should decide whether a horse needs it, which product to use, and for how long.
Disclaimer: This article is for general education only and is not veterinary advice.
Always consult a licensed veterinarian before giving nandrolone or any medication to your horse.
What Is Nandrolone for Horses?
Nandrolone is an injectable anabolic-androgenic steroid derived from testosterone (a 19-nortestosterone). It binds androgen receptors, which promotes protein building and nitrogen retention, and it can also stimulate red blood cell production.
Vets may call it an anabolic steroid for horses when they want to support body condition during illness or recovery.
It is sold as long-acting oil-based injections, most often as nandrolone decanoate (the human brand is Deca-Durabolin) or nandrolone laurate. The ester is the part of the molecule that controls how slowly the drug is released from the muscle.
What Is Nandrolone Used For in Horses?
The veterinary reference we reviewed lists equine anabolic support, mainly for debility and anaemia. In practice, a vet might consider it in these situations:
- Weight and muscle loss linked to long-term illness
- Recovery after surgery or a prolonged lay-up
- Anaemia, as an add-on while the underlying cause is treated
- Older, debilitated horses that are losing condition
One honest limit: there are no large controlled clinical trials that prove how well nandrolone works in sick horses. Most equine data comes from pharmacology and doping-control studies, so dosing guidance rests on formularies and vet experience rather than on trial results.
It never replaces treating the cause of the weight loss or anaemia.
Nandrolone Dosage Chart for Horses
The reference dose is 1 mg per kg of body weight, intramuscularly, every 4 weeks. The chart below converts that into total milligrams and millilitres for the two most common concentrations, 50 mg/mL and 100 mg/mL. It is a maths aid, not a prescription.
| Body weight | Total dose | Volume at 50 mg/mL | Volume at 100 mg/mL |
|---|---|---|---|
| 200 kg (441 lb), small pony | 200 mg | 4 mL | 2 mL |
| 300 kg (661 lb) | 300 mg | 6 mL | 3 mL |
| 400 kg (882 lb) | 400 mg | 8 mL | 4 mL |
| 500 kg (1,102 lb) | 500 mg | 10 mL | 5 mL |
| 600 kg (1,323 lb) | 600 mg | 12 mL | 6 mL |
How to Calculate the Dose Step by Step
This is the same maths your vet uses, and it helps you catch a decimal-point error. For another worked example of weight-based dosing, see our Bute guide.
- Weigh the horse. Use a scale or a weight tape. Guessing by eye is a common source of error.
- Multiply by the mg/kg dose. 500 kg × 1 mg/kg = 500 mg.
- Read the concentration on the vial. Look for mg per mL, such as 50 mg/mL or 100 mg/mL.
- Divide milligrams by concentration. 500 mg ÷ 50 mg/mL = 10 mL. At 100 mg/mL it is 5 mL.
- Check it against your vet’s written instructions before drawing up anything.
Why Doses Differ Between Products
Never copy a dose from one product or species to another. Nandrolone comes in different esters and strengths, and some horse products mix it with other hormones.
One Australian equine tissue-repair injection, for example, combines nandrolone decanoate with oestradiol and a progestogen, and its label directs 1 mL per 100 kg every 2 weeks. That is a different product with a different schedule from the single-ingredient 1 mg/kg reference above.
Small-animal products show the same gap. A European nandrolone laurate product for dogs and cats is dosed at 2 to 5 mg/kg every 3 to 4 weeks, which is far above the equine reference. The takeaway is simple: follow the label and prescription for your exact product.
Nandrolone Horse Dosage Calculator
Enter your horse’s weight and the strength printed on the vial. The calculator is fixed at the 1 mg/kg reference dose, so it cannot be used to work out a higher amount.
Nandrolone Dosage Calculator for Horses
Equine anabolic support: 1 mg/kg IM every 4 weeks (debility, anaemia; Schedule III).
Calculated dose
How Often Can a Horse Have Nandrolone?
The reference interval for horses is every 4 weeks. In small-animal references, courses rarely run beyond 2 to 3 months because response fades and liver effects become more of a concern, and vets often apply similar caution to horses. How long a course lasts is a vet call based on bloodwork and how the horse responds.
How Is Nandrolone Given to Horses?
Nandrolone is given as a deep intramuscular injection. The oil base is thick, so the vial is usually warmed slightly before use. Injection sites should be rotated to cut the risk of sore spots, abscesses and granulomas.
- Let your vet or a trained person give the injection.
- Keep each dose in the vet’s recorded schedule so intervals are never shortened by mistake.
- Keep the vial locked away. It is a controlled drug in many places, and records may be required.
- Follow the label’s handler warnings. Pregnant women and anyone with a steroid sensitivity should take particular care and should ask their own doctor if unsure.
Nandrolone Side Effects and Risks in Horses
The main concerns are injection-site reactions, liver effects, fluid retention, behaviour change and hormonal effects. Detailed equine safety data is limited, so much of this list comes from veterinary formulary data that covers the drug more broadly.
When Nandrolone Should Not Be Used
Veterinary formularies list several absolute contraindications. Equine-specific data is thin, so most vets treat these as applying to horses too:
- Pregnancy, because androgens can virilise the foal
- Lactation
- Liver disease
- Severe heart disease
- Known allergy to nandrolone or the oil carrier
- Use to boost athletic or breeding performance
Drug Interactions to Raise With Your Vet
Formulary data lists a few interactions. Anabolic steroids can strengthen the effect of anticoagulants, raise blood glucose and work against insulin or oral diabetes drugs, and add to the sodium retention seen with corticosteroids. They can also alter thyroid test results.
If your horse is on a corticosteroid such as dexamethasone (see our dexamethasone dosage for horses guide) or on metformin for insulin resistance (see our metformin dosage for horses guide), tell your vet before nandrolone is started.
Monitoring Checklist
- Baseline blood count and biochemistry before the first dose
- Rechecks at about 4 and 8 weeks, as small-animal guidance suggests
- Liver enzymes at intervals your vet sets
- Weight and body condition score every week or two
- Behaviour, appetite, swelling and injection-site notes
Nandrolone, Competition and Drug Testing
Nandrolone is an anabolic steroid, and racing and equestrian authorities treat it as a prohibited substance. Rules and thresholds differ by sport and country, so check your governing body’s current list before any treatment. Never assume a horse is “clean” after a certain number of days.
A study in Drug Testing and Analysis gave three retired Thoroughbred geldings weekly injections of nandrolone decanoate for three weeks. Nandrolone decanoate and most identified metabolites were still detectable in plasma at least 20 days after the last injection, when sampling ended.
Nandrolone itself was not found in urine, but its breakdown products were. Detection time depends on the dose, ester and individual horse, so no single withdrawal number is safe to quote.
Food-animal rules also matter. Product labels for equine anabolic injections often state they must not be used in horses that may be slaughtered for human consumption. Check the label and your local rules.
Nandrolone vs Other Ways to Support a Run-Down Horse
| Approach | What it does | Main limit |
|---|---|---|
| Treat the underlying cause | Fixes why the horse is losing condition (parasites, dental pain, infection, organ disease) | Needs a proper vet work-up |
| Feeding and management review | Adds calories, protein and better forage in a controlled way | Slower, and only works if intake is the problem |
| Nandrolone (vet-prescribed) | Supports protein building and red cell production | Side effects, testing rules, limited equine trial data |
Check the basics first. Worm burdens and gastric ulcers are common reasons for poor condition, and our fenbendazole dosage for horses and omeprazole dosage for horses guides cover those treatments.
Common Mistakes to Avoid
- Mixing up milligrams and millilitres
- Using the wrong vial strength in the calculation
- Estimating weight instead of measuring it
- Repeating the injection early because the horse “looks the same”
- Skipping bloodwork
- Ignoring testing rules for competition horses
Questions to Ask Your Vet Before Starting
FAQs
What is nandrolone used for in horses?
Vets may use nandrolone as anabolic support for debilitated horses and as an add-on in some cases of anaemia. It does not replace diagnosing and treating the underlying cause of weight loss or poor condition.
What is the nandrolone dose for horses?
One veterinary reference lists 1 mg per kg of body weight by intramuscular injection every 4 weeks. Your vet sets the actual dose based on the product, the horse and the condition being treated.
How much nandrolone does a 500 kg horse get?
At the 1 mg/kg reference dose, a 500 kg horse works out to 500 mg. That is 10 mL of a 50 mg/mL product or 5 mL of a 100 mg/mL product. Always confirm the vial strength and your vet’s written instructions first.
How often can a horse have nandrolone?
The reference interval is every 4 weeks. In small-animal references, courses rarely run beyond 2 to 3 months, and equine vets usually apply similar caution. Your vet decides based on bloodwork and response.
How is nandrolone given to a horse?
It is given as a deep intramuscular injection of an oil-based solution. Injection sites are rotated to lower the risk of local reactions such as abscesses or lumps.
What are the side effects of nandrolone in horses?
Listed effects include injection-site reactions, raised liver enzymes, sodium and water retention, behaviour changes and hormonal effects. Equine safety data is limited, so monitoring with your vet is important.
Can pregnant mares receive nandrolone?
No. Pregnancy is listed as an absolute contraindication in veterinary references because androgens can virilise the foetus. Lactation is also listed as a contraindication.
Can racehorses or competition horses have nandrolone?
Racing and equestrian authorities treat nandrolone as a prohibited anabolic steroid. Check your governing body’s current rules and speak with your vet before treating any horse that competes.
How long does nandrolone stay in a horse’s system?
There is no single safe number. In one study of three geldings given weekly injections for three weeks, nandrolone decanoate and most metabolites were still detectable in plasma at least 20 days after the last injection, when sampling stopped.
Is nandrolone the same as Deca-Durabolin?
Deca-Durabolin is a brand name for nandrolone decanoate. Veterinary products may use nandrolone decanoate or nandrolone laurate, and strengths and labels differ, so do not swap products without your vet.
Do I need a prescription to buy nandrolone for my horse?
In many countries nandrolone is a prescription-only controlled drug with storage and record rules. One reference lists it as Schedule III. Rules vary by country, so confirm with your vet and local regulator.
Can horses treated with nandrolone go into the food chain?
Labels on equine anabolic injections commonly state they must not be used in horses that may be slaughtered for human consumption. Always read the product label and follow local food-animal rules.
Will nandrolone make my thin horse gain weight?
It supports protein building, but large equine trials are lacking and it is not a fix for the cause of weight loss. Dental problems, parasites, pain, poor feed and illness should be investigated first.
Bottom Line and Next Steps
Nandrolone can help support condition in some debilitated horses, but it is a controlled steroid with real trade-offs. The reference dose of 1 mg/kg every 4 weeks is only useful once you know your horse’s true weight, the vial strength and your vet’s plan.
- Book a vet exam to find the cause of weight loss or anaemia first.
- Ask for the dose written in both mg and mL.
- Agree on bloodwork and a stop date before the first injection.
- Check competition and food-animal rules before treating.
This article is general information for horse owners and is not veterinary advice. Dosing, product choice and legality depend on your horse, your vet and your country.
