A young guinea pig grows fast in its first three months, and a simple weekly record turns that growth into something you can actually see. Memory blurs week to week, but a written line of weights, appetite notes, and small observations will flag a stall or a problem days before it becomes obvious just from looking.
Weigh the same way, at the same time, every week
Use a kitchen scale with a bowl or low box lined with fleece so the youngster sits still and feels secure. Weigh before the morning feed, on the same weekday, and write the result down immediately rather than trusting that you will remember the trend. What you are watching for is a steady upward pattern, not a particular target number, because littermates and different breeds gain at different rates.
A single flat week in an otherwise bright, eating youngster can simply be a pause. Weight loss, or a flat week combined with less interest in food, is a different signal and should prompt a call to a veterinarian rather than another week of waiting.
Record eating and droppings alongside the number
Note how much hay is disappearing, whether fresh vegetables are eaten eagerly or left, and whether the youngster is drinking normally. Guinea pigs cannot make their own vitamin C, so recording which vitamin C rich foods were offered and actually eaten is a genuinely useful part of this check, not a detail. Droppings tell their own story: plentiful, uniform pellets suggest the gut is moving well, while a sharp drop in quantity, very small pellets, or soft droppings deserve a note and close watching.
If eating slows, offer familiar favourites and check the mouth area, then contact a veterinarian if intake does not recover quickly, because a guinea pig that stops eating can decline fast.
Check teeth, coat, eyes, and movement by hand
Run a gentle hand over the body each week to feel ribs, spine, and any new lumps under the skin while the coat is still short enough to make that easy. Look at the front teeth where they meet: they should align evenly rather than slanting or overgrowing on one side, and drooling or dropping half-chewed food can point to a mouth problem worth a veterinary look.
Check that eyes are clear and dry, ears are clean, nails are not curling into pads, and the youngster moves on all four feet without limping or dragging. Note confidence too: a young guinea pig that comes forward at the rustle of a food bag is showing you something different from one that has started hiding through feeding time.
Keep the record where it will be used
A notebook that stays in a drawer helps nobody at a checkup. Keep the weekly lines together with vaccination or parasite treatment notes, the food brand-free details such as hay type and vegetable rotation, and the date of the first health check, so patterns are visible at a glance. Sharing those notes with whoever feeds the youngster while you are away also prevents double feeds and missed changes.
Those weekly weights and observations become far more useful when they travel with the guinea pig instead of staying at home, and KinsLe Pet Passport gathers the growth record and health notes into one packet you can hand over at any appointment.