A national shortage of hormone replacement therapy (HRT) could affect hundreds of thousands of menopausal women in the UK.

Around half of the most commonly prescribed HRT products, which replace hormones including oestrogen that naturally decline during menopause, are out of stock.

The high street pharmacies Boots and Lloyds are among those said to be experiencing shortages.

The Department for Health and Social Care said it was aware of ongoing supply issues caused by manufacturing delays. A spokesperson said: “We are working closely with all suppliers to maintain overall flow of medicines to patients.

“Supplies of alternative HRT products are available and any patient affected should discuss alternatives with their doctor.”

The department initially became aware of the problem in December, but shortages have worsened in recent weeks.

Lloyds’ supplier AAH Pharmaceuticals has run out of 15 of the 24 HRT brands it stocks, according to figures given to the Daily Mail. The pharmaceutical retailer Alliance, which is owned by the same group as Boots, has run out of nine of 27 HRT products.

Prof Helen Stokes-Lampard, the chair of the Royal College of GPs, said the real reason for the shortages was unclear.

Speaking to BBC Radio 4’s PM programme, she said: “We know that there are the generic phrases like ‘supply issues’ and ‘manufacturing problems’. “But because it’s commercially sensitive ... nobody will be honest with the public and the NHS. So it’s frustrating.”

Stokes-Lampard encouraged women to get their repeat prescriptions for the products earlier than usual. She said that if their pharmacies were out of stock of their usual product, they should ask pharmacists about alternatives and inform their GP.

For women experiencing the menopause, HRT is the most common form of treatment for symptoms including hot flushes, night sweats and vaginal dryness.

Products come as tablets, skin patches, gels, vaginal creams, pessaries and rings.

According to the National Institute for Health and Care Excellence, around a million women in the UK use treatment for symptoms of the menopause.

• This article was amended on 13 August 2019 to remove an inaccurate statement that the shortage could affect almost all menopausal women in the UK.