Worming tablets for small dogs and large dogs — getting the dose right

Quick answer. UK wormers are dosed by body weight, not by breed size. The standard rule across most UK products is 1 tablet per 10 kg of body weight. For dogs under 10 kg, scored tablets split into halves or quarters give accurate small-dog dosing — a 2.5 kg Chihuahua takes a ¼ tablet; a 5 kg Yorkie takes ½. For dogs over 30 kg, “XL” formulations exist (Drontal Plus XL, larger Milbemax) that contain higher per-tablet strengths so you don’t have to give 4+ standard tablets. Biheldon uses standard-strength scored tablets — a maximum of 4 tablets per animal per dose covers dogs up to 50 kg.

The “I have a small dog — do I need a special wormer” and “I have a big dog — do I need an XL” questions are two of the most-asked dosing questions in UK pet ownership. The honest answer is the same for both: most modern wormers are dosed by weight, the standard formulation covers a wide range, and the only cases where you genuinely need a different product are at the extremes (very small puppies and giant breeds over 30–50 kg).

The basic rule — 1 tablet per 10 kg

Almost every UK wormer at standard strength follows the same dosing rule: 1 tablet per 10 kg of body weight. This applies to Biheldon, Drontal Dog Tasty Bone (standard), Milbemax for adult dogs, and Drontal Cat. The differences between products are about active ingredient and parasite cover, not about dosing arithmetic.

The reason the rule is consistent is that the body-weight–to–parasite-burden relationship is reasonably linear — a 20 kg dog usually carries roughly twice the parasite mass of a 10 kg dog of the same lifestyle. The drug dose needs to scale to clear all of it.

The Biheldon dosing chart by body weight

This is the same chart that appears on every Biheldon box and on the product page:

Maximum 4 tablets per animal per dose. For dogs over 50 kg, talk to your vet about an XL formulation.

Small dogs (under 10 kg) — the scored-tablet question

Small-dog dosing is where the scored tablet matters. A tablet that is genuinely scored — i.e. there is a visible groove deep enough to break cleanly when pressed — can be split into halves or quarters that each deliver an accurate portion of the active ingredient. Biheldon’s tablets are scored on both sides specifically for this reason.

The accuracy of split-tablet dosing matters because:

• Under-dosing doesn’t clear the parasite burden — eggs continue to be shed and the worming “fails”
• Over-dosing is rarely dangerous with praziquantel + pyrantel embonate (both have very wide safety margins) but is unnecessary and wastes tablet

What about products that aren’t scored? Drontal Cat is unscored — splitting it gives an approximate dose at best. For small cats, this is one of the reasons some owners prefer Biheldon’s scored format. Milbemax for small dogs is a different (lower-strength) tablet rather than a split of the larger one, so there’s no scored-tablet question for that range.

Very small dogs and puppies — under 2.5 kg

For pets under 2.5 kg, the standard quarter-tablet dose is the smallest accurate split you can reliably do at home. Below that — newborn or very young puppies under a few weeks old — most UK wormers are not licensed at all. The standard puppy worming start is 4 weeks of age, by which point most puppies are above the minimum body-weight threshold for a quarter-tablet dose. For puppies under that, your vet may prescribe a fenbendazole suspension (Panacur Puppy 2.5% suspension) which is dosed by millilitre and lets you go below the tablet thresholds.

See our worming frequency pillar guide for the full puppy schedule.

Large dogs (20–40 kg) — multi-tablet dosing

For dogs between 20 and 40 kg, the standard Biheldon approach is multi-tablet dosing — 2, 2½, 3, or 3½ tablets given as a single combined dose. There is no clinical issue with this; the tablets are designed to be combinable. You can give them all at once with food, broken into a couple of mouthfuls, or one at a time over a few minutes.

The practical question owners ask is whether to switch to an XL formulation at this weight. The answer depends on the product:

• Biheldon — no XL formulation exists. The standard-strength scored tablet covers dogs up to 50 kg via multi-tablet dosing.
• Drontal — Drontal Plus XL exists at higher per-tablet strengths (525 mg febantel + 504 mg pyrantel embonate + 175 mg praziquantel per tablet) for dogs over 35 kg. Saves you giving 4 standard tablets, but the per-tablet price is higher (£6.99+ vs £2.69).
• Milbemax — a separate “for large dogs” (25 kg+) formulation exists, again at higher per-tablet strength.

For dogs up to 50 kg, Biheldon at 4 tablets per dose is a perfectly valid option. For giant-breed dogs above 50 kg, talk to your vet — most will recommend an XL product for accuracy.

Very large and giant-breed dogs (over 50 kg)

For dogs over 50 kg — Great Danes, large Saint Bernards, English Mastiffs, some New foundland s and Leonbergers — the standard Biheldon dosing chart caps out. The labelled maximum of 4 tablets per animal per dose is a safety ceiling, not a measure of clinical adequacy at very large body weights.

For dogs in this range, options include:

• Drontal Plus XL at 1 tablet per 17.5 kg (so 3 tablets for a 50 kg dog, 4 tablets for a 60–70 kg dog)
• Milbemax for large dogs dosed by weight
• A vet-led plan that may use a different active or off-label dosing

This is a sensible “ask your vet” situation rather than a “buy more tablets” one.

Split-tablet storage

If you’re splitting a Biheldon tablet for a small dog or cat, you’ll have a partial tablet left over. The scored design makes the splits clean; storage practicalities:

• Use within 28 days ideally — return the split tablet to the original blister or to a small airtight container
• Store at room temperature (below 25°C) in the original packaging or equivalent
• Don’t store split tablets in a hot or humid area — humidity affects pyrantel embonate stability over time

A 30-tablet box of Biheldon used for a single ½-tablet-per-3-months indoor cat will last roughly 15 years — long enough that you should be ordering fresh, not preserving splits indefinitely.

Multi-pet households — different sizes, same product

The strongest practical case for a scored single-strength wormer is the multi-pet, multi-size household. A 25 kg Cocker Spaniel + a 4 kg Cat + a 6 kg small terrier all use the same Biheldon box:

• Cocker Spaniel: 2½ tablets quarterly = 10 tablets per year
• Cat: ½ tablet quarterly = 2 tablets per year
• Terrier: 1 tablet quarterly = 4 tablets per year
• Total: 16 tablets per year — about half of a 30-tablet box across three pets

This is what the single-source-of-dosing approach is designed for, and it is why the per-tablet price difference between Biheldon (£0.50) and Drontal (£2.51-£2.69) compounds meaningfully across the household.

What you should NOT do

A few common mistakes worth flagging:

• Don’t dose by breed instead of by weight. A “small” terrier breed can weigh anywhere from 3 to 12 kg depending on individual variation. Weigh the dog (or cat) and dose by the number, not the breed name.
• Don’t round up substantially “to be safe”. A dog at 19 kg should take 2 tablets, not 2½. Over-dosing isn’t dangerous with praziquantel + pyrantel embonate but it’s still wasteful.
• Don’t skip the partial tablet for a small dog. A 4 kg dog given a full 1-tablet dose (intended for 10 kg) is being given 2.5× the labelled dose. With Biheldon that is still within safety bounds, but it’s not necessary and isn’t best practice.
• Don’t use a cat-only product on a small dog or vice versa at random — most UK wormer actives are common across species, but the formulations and strengths differ between Drontal Cat and Drontal Dog products. Biheldon is licensed for both species, so the same tablet works either way.

The bottom line

UK wormers are dosed by body weight, at the standard rate of 1 tablet per 10 kg. Biheldon’s scored tablets cover dogs and cats from 2.5 kg to 50 kg with accurate half- and quarter-tablet splits for small pets. For dogs over 50 kg, XL formulations (Drontal Plus XL, larger Milbemax) save you giving 4+ standard tablets, at a higher per-tablet price. For very young puppies under the tablet thresholds, fenbendazole suspension (Panacur) is the standard vet choice.

Weigh your pet, follow the dosing chart, split the tablet cleanly along the score line for small pets, and use the single-strength tablet for any multi-pet household. That’s the whole picture.

See the full Biheldon dosing chart, the Biheldon vs Drontal comparison for the standard-vs-XL question across products, and the worming frequency pillar guide for the schedule by lifestyle.

Tags: #dogs#dosing#small-dogs#large-dogs