Old age in a guinea pig arrives as a collection of small, gradual shifts: she moves more deliberately, sleeps in longer stretches, feels bonier over the hips, and takes her time over hay she once demolished. None of those alone confirms a problem, but together they mark the senior stage, when closer watching and gentler housing start to matter.
Body and weight changes you can feel
Run your hands gently over her weekly. Senior guinea pigs commonly lose muscle along the back and hindquarters, so the spine and hip bones feel more prominent even when the belly still looks round. Fur often thins, turns coarser, and greys around the chin and muzzle.
Weekly weighing gives those impressions a number. A slow drift downward over months fits ageing; a sharp drop over a week or two does not, and deserves a vet visit even if she still comes forward for vegetables. Keep the weights in order, because the trend is far more telling than any single reading.
Movement, feet, and comfort
An older guinea pig may hesitate at a ramp she once charged up, shuffle rather than scamper, and choose one level of her home for most of the day. Nails grow into less wear as activity falls, so they need trimming more often, and feet should be checked for redness or sore patches from sitting longer in one place.
Soften her world accordingly: fleece or deep bedding under favourite resting spots, food and water within a short, flat walk, and no essential item placed where she must climb to reach it.
Eyes, teeth, appetite, and digestion
Eyes may look cloudy in old age, and some seniors navigate mainly by familiar layout, which is why rearranging the enclosure can unsettle them. Appetite often narrows rather than vanishing: she may favour soft vegetables, leave long hay strands, or eat pellets slowly, all of which can point to teeth that need checking as much as to age itself.
Droppings may become slightly smaller or less even as gut movement slows, but a day of far fewer droppings, or eating almost nothing, is never something to file under old age. Guinea pigs need food moving through them steadily, and a senior who stops eating needs same-day veterinary advice.
Behaviour and sleep
Expect longer, deeper rest, less interest in exploring a playpen, and more pleasure in familiar comforts: a warm hide, a favourite food offered by hand, a quiet lap. She may wheek less loudly or come forward more slowly, yet still clearly enjoy those moments, and that enjoyment is an important part of judging how she is doing.
Sudden hiding, a hunched posture with a puffed coat, grinding sounds, or unusual quietness point the other way. Those are discomfort signs at any age, and in a senior they should prompt a quick call rather than watchful waiting.
Noting dates beside weights, appetite changes, and new lumps or sore spots turns vague worry into a clear story for your vet. Keep the enclosure layout steady between checks, so any new hesitation reflects her body rather than a moved hide or bowl. KinsLe Pet Passport keeps that record together in one portable packet, ready to bring along whenever a change needs checking.