Many older people said they felt "abandoned" during the first lockdown, according to a survey by Age Cymru.
The charity also said more than two-thirds of older people struggled to access healthcare.
Seventy-eight per cent of respondents to the survey said the biggest challenge for them was not being able to see family and friends.
The Welsh Government said people's contributions could help plan for the months ahead.
The survey also found extra pressure had been put on older carers who were struggling with less support.
A respondent in her late eighties said she had not received any help with caring for her husband 24 hours a day since 17 March.
"The strain is immense," she said.
Thirty-two per cent of respondents said they were lonely, rising to 55% amongst those living alone.
One Powys contributor in their late seventies told the survey: "I have lost my voluntary work and classes and am on my own 24/7. Often feel suicidal."
Tony Price, 64, from Cardiff, cares for his wife Tina, who has had several strokes and was stabbed in the neck in February.
Mr Price, who served with the Welsh Guards for 22 years, had a knee operation in January but is in "constant pain" and has struggled to get the aftercare he needs.
His last hospital appointment was in March before lockdown began.
He said his GP had been "brilliant" during appointments over the phone, but was only able to prescribe morphine, which he has been taking for three months.
He had a telephone consultation with the hospital but it was not what he felt he needed, and anxiety about what might be wrong has also affected him.
"We should have the opportunity to go into the hospital. I know people are afraid of Covid-19 but it's really a struggle for me at the moment."
Cardiff and Vale University Health Board said it had been working to maintain hospital services as far as possible.
"We are sorry to hear that Mr Price feels that he hasn't been unable to fully access the care he needs. We would urge any patients who are worried about their health to contact their healthcare professional... and raise any concerns about the care they receive with our concerns team."
The Age Cymru survey suggested 70% of older people in Wales had difficulty in accessing hospital, GP, dentist and chiropody appointments.
Other issues raised included scams, job losses and reduced public transport.
Age Cymru's chief executive Victoria Lloyd said that research highlighted "real hardships" for older people.
"Not being able to access the healthcare they need, when they need it, could result in many older people suffering with an unnecessary deterioration in their health.
"Similarly, older carers left to cope on their own with very challenging caring responsibilities could find themselves exhausted and incapable of providing any sort of care in the months ahead.
"With winter coming we need a concerted effort to make sure that we have the right systems and support in place for older people."
Deputy Minister for Health and Social Services Julie Morgan said: "No-one should feel invisible or abandoned because of their age - we must work across generations to reconnect, build confidence and challenge ageist stereotypes."