The most common causes of low blood pressure in women are pregnancy, heavy menstrual bleeding and the anaemia that follows it, dehydration, standing up suddenly or standing for a long time, intense heat, and certain medicines such as diuretics, blood pressure medicines and some antidepressants. Less often, low blood pressure points to a health problem that needs testing, such as a thyroid or adrenal disorder, a heart condition, a severe infection or a severe allergic reaction.
Low blood pressure usually means a reading below 90/60 mmHg, but the number alone does not decide how serious it is. Some women live with naturally low pressure and no symptoms at all, while others feel very dizzy after a small drop from their usual level. What matters is the symptoms that come with it and the cause behind it, which this article explains step by step.
Causes of low blood pressure in women
Women face several factors of their own that make low blood pressure more frequent, on top of the general causes that affect everyone. Here are the most important, starting with the most common:
1. Pregnancy
During pregnancy the circulation expands quickly to supply the baby, and pregnancy hormones relax the walls of the blood vessels, so blood pressure often falls in the first and second trimesters and gradually returns towards normal near delivery. In the last months, the womb can press on the large vein returning blood to the heart when the woman lies on her back, causing dizziness and nausea; lying on the left side usually helps. It is important to know that dizziness with abdominal pain or vaginal bleeding in pregnancy, or when pregnancy is possible (for example a late or missed period), is not normal: it can signal internal bleeding, such as an ectopic pregnancy, and needs emergency care immediately.
2. Heavy periods and anaemia
Heavy or prolonged monthly bleeding gradually leads to iron deficiency and anaemia, which reduces the blood's ability to carry oxygen and brings dizziness, fatigue, a pale face and a fast heartbeat. Severe period pain can also trigger a vasovagal reaction, a temporary drop in blood pressure and pulse in response to pain. However, fainting, or severe abdominal pain with dizziness when pregnancy is possible, needs emergency care immediately, because it can signal internal bleeding. Anaemia can also come from a lack of vitamin B12 or folic acid, or from a poor diet.
3. Dehydration and low fluid intake
When the body loses more fluid than it takes in, blood volume falls and so does blood pressure. This happens with vomiting and diarrhoea, heavy sweating in hot weather, long fasting without enough fluid to make up for it, breastfeeding while drinking too little water, and very strict diets.
4. Orthostatic (postural) hypotension
This is a drop in blood pressure within a few minutes of moving from sitting or lying down to standing, causing blurred vision, dizziness and sometimes a fall. It is more likely with dehydration, long periods of inactivity and older age. A related condition, postural orthostatic tachycardia syndrome (POTS), is more common in young women and is marked by a clear rise in heart rate with dizziness and fatigue on standing.
5. Certain medicines
Many people overlook the fact that some medicines lower blood pressure as a side effect, including diuretics, all types of blood pressure medicines, some antidepressants, nitrates used for heart disease, some sedatives and sleeping medicines, and some Parkinson's disease medicines. If you notice dizziness after starting a new medicine or a change in how you take it, do not stop it on your own; see your doctor, who will decide on the right adjustment.
6. Hormone and gland disorders
Gland disorders affect women more often than men. They include an underactive thyroid, which slows the pulse and sometimes lowers blood pressure, and adrenal insufficiency, which causes low pressure with severe fatigue, weight loss and salt cravings. Low blood sugar can cause symptoms that mimic low blood pressure, such as dizziness, shaking and sweating, especially in women with diabetes. A woman with diabetes who becomes shaky, sweaty, confused or drowsy should check her blood sugar if she can and follow her doctor's plan for low sugar; if she is confused, drowsy or cannot swallow, call an ambulance immediately. Hot flushes around menopause can briefly widen the blood vessels and cause mild dizziness in some women.
7. Heart problems
A very slow heartbeat, rhythm disturbances, heart valve problems and a weak heart muscle can all reduce how much blood the heart pumps, lowering blood pressure. These causes in particular need medical assessment when low pressure comes with palpitations; if it comes with chest pain, pressure or tightness, shortness of breath or fainting, call an ambulance or go to the emergency department immediately.
8. Other causes
- Eating disorders and severe weight loss, which weaken the body and upset its salt balance.
- Low blood pressure after large meals, especially in older women, because blood is diverted to the gut.
- Standing for a long time in a hot place, or long, very hot baths or showers.
- Nerve conditions that affect blood pressure control, such as diabetic neuropathy.
- Bleeding after childbirth or after surgery.
Causes of a sudden drop in blood pressure
A sudden drop is different from long-standing low blood pressure, because it can be a sign of a condition that needs prompt treatment. Its main causes include heavy bleeding, whether visible or internal; severe dehydration after repeated vomiting or diarrhoea; serious infection that may progress to sepsis; a severe allergic reaction to a sting, food or medicine; sudden heart rhythm disturbances; standing up quickly after lying down for a long time; and a vasovagal faint, which can happen with severe pain, fear or the sight of blood. In a pregnant woman, internal bleeding such as an ectopic pregnancy must always be considered.
Symptoms of low blood pressure in women
Symptoms are similar in women and men, but women may notice them more around periods or during pregnancy. The main ones are:
- Dizziness or light-headedness, especially on standing.
- Blurred or dimmed vision.
- Nausea.
- Fatigue, general weakness and poor concentration.
- Cold hands and feet and a pale face.
- A fast heartbeat or palpitations.
- Headache and thirst.
- Fainting or feeling about to faint.
When is low blood pressure an emergency?
Before trying anything at home, call an ambulance or go to the emergency department immediately if low blood pressure comes with any of the following:
- Fainting or loss of consciousness, even if she comes round quickly.
- Chest pain, pressure or tightness, or shortness of breath.
- Confusion or difficulty speaking, or weakness or numbness on one side of the body.
- Cold, pale, sweaty skin with a fast, weak pulse.
- Heavy bleeding from anywhere, vomiting blood, or black stools.
- A high fever together with low blood pressure.
- Swelling of the face, lips or throat, or difficulty swallowing, after contact with something that can cause allergy.
- Dizziness with abdominal pain or vaginal bleeding in pregnancy, or when pregnancy is possible (for example a late or missed period).
Do not rely on a home blood pressure reading to rule out danger: any of these signs is enough to call an ambulance or go to the emergency department immediately, whatever the reading says.
What to do when blood pressure drops suddenly
If none of the emergency signs above is present, the dizziness is mild and she is fully alert, these steps can help:
- Sit or lie down at once to avoid falling, and raise the legs above heart level if possible.
- Do not stand until the dizziness has fully passed, then get up slowly in stages.
- Drink water or other fluids if she is alert and able to swallow; never give anything by mouth to someone who has lost consciousness.
- Move away from heat and loosen tight clothing.
- Do not drive or climb stairs until fully recovered.
If symptoms do not improve within a short time, or the episodes keep coming back, it is important to see a doctor to find the cause.
Treating low blood pressure in women according to the cause
There is no single treatment for everyone, because treatment is aimed mainly at the cause. Low pressure from dehydration improves when fluids are replaced; anaemia is treated by finding its cause, such as managing heavy periods and replacing missing iron or vitamins as your doctor prescribes. If a medicine is the cause, the doctor may change its type or timing or switch it. Gland and heart conditions have their own specialist treatment after diagnosis.
For long-standing low blood pressure with repeated symptoms, a doctor may advise:
- Drinking more fluids spread through the day.
- Adding salt to food only to the extent your doctor sets, since this is not suitable for women with heart or kidney disease or with high blood pressure at other times.
- Wearing compression stockings to help blood return from the legs.
- Eating several small meals instead of large ones.
- Raising the head of the bed slightly and sitting on the edge of the bed before standing in the morning.
- Regular, moderate physical activity to improve the fitness of the circulation.
In selected cases a doctor may prescribe medicines that raise blood pressure, such as medicines that help the body hold on to fluid and salt or that tighten the blood vessels. These are taken only as your doctor prescribes, with follow-up.
Herbs and drinks to raise blood pressure: what is true?
Many home remedies claim to raise blood pressure, but no herb has been shown to be a safe treatment for low blood pressure. Coffee and other caffeinated drinks may raise blood pressure briefly, but they do not treat the cause and can add to dehydration if overused. Liquorice can genuinely raise blood pressure, but too much of it can cause low potassium, heart rhythm problems and swelling, so it is not advised as a way to treat low pressure without a doctor's advice. Ordinary fluids and a balanced diet remain the basis, together with treating the real cause.
Diagnosis and follow-up
A doctor usually starts with detailed questions about the symptoms, when they happen and how they relate to standing, periods or pregnancy, and reviews the medicines the woman takes. Blood pressure is then measured lying down and again standing to detect postural hypotension. Tests may include a full blood count for anaemia, iron stores, thyroid function, blood sugar and salts, and if fainting keeps recurring, an ECG, a heart ultrasound (echocardiogram) or a tilt-table test. Keeping a home record of blood pressure readings alongside symptoms and showing it to the doctor helps find the cause.
Everyday tips to prevent low blood pressure
- Drink fluids regularly, and more in hot weather, while breastfeeding and when unwell.
- Avoid standing still for long periods, and move your leg muscles while standing.
- Change position slowly, from lying to sitting and then to standing.
- Eat a balanced diet rich in iron and vitamins, and do not skip meals.
- Have heavy periods checked by a doctor rather than treating them as normal.
- Review your medicines with your doctor if dizziness starts after a new medicine.
- Attend regular antenatal check-ups and tell your doctor about repeated dizziness.
Frequently Asked Questions
What are the causes of low blood pressure?
Common causes of low blood pressure include dehydration and low fluid intake, standing up suddenly or for a long time, intense heat, anaemia, and some medicines such as diuretics, blood pressure medicines and some antidepressants. It can also come from health problems that need testing, such as thyroid or adrenal disorders, heart conditions, severe infection or severe allergy. In women, pregnancy and heavy periods are added to the list of common causes.
What are the symptoms of low blood pressure in women?
Symptoms of low blood pressure in women include dizziness or light-headedness, especially on standing, blurred vision, nausea, fatigue and poor concentration, cold hands and feet with a pale face, a fast heartbeat, headache and thirst, and feeling about to faint. Call an ambulance or go to the emergency department immediately if low pressure comes with any of the following: fainting or loss of consciousness, even briefly; chest pain, pressure or tightness; shortness of breath; confusion, difficulty speaking, or weakness or numbness on one side of the body; cold, pale, sweaty skin with a fast, weak pulse; heavy bleeding from anywhere, vomiting blood or black stools; a high fever with low blood pressure; swelling of the face, lips or throat or difficulty swallowing after contact with something that can cause allergy; or dizziness with abdominal pain or vaginal bleeding in pregnancy, or when pregnancy is possible (for example a late or missed period).
What are the causes of low blood pressure in women and its treatment?
The main causes of low blood pressure in women are pregnancy, heavy periods and anaemia, dehydration, standing up suddenly or for a long time, some medicines, and gland or heart conditions. Treatment depends on the cause: replacing fluids for dehydration, treating the cause of anaemia and replacing iron or vitamins as your doctor prescribes, and having the doctor adjust a medicine that causes it rather than stopping it yourself. For long-standing low pressure, a doctor may advise more fluids, extra salt only as much as they set, compression stockings and smaller meals, and in selected cases may prescribe medicines that raise blood pressure, taken as your doctor prescribes.
What are the causes of a sudden drop in blood pressure?
Causes of a sudden drop in blood pressure include heavy visible or internal bleeding, severe dehydration after repeated vomiting or diarrhoea, serious infection, severe allergy, heart rhythm disturbances, standing up quickly after lying down for a long time, a vasovagal faint with pain or fear, and in pregnancy internal bleeding such as an ectopic pregnancy. Call an ambulance or go to the emergency department immediately if the drop comes with any of the following: fainting or loss of consciousness, even briefly; chest pain, pressure or tightness; shortness of breath; confusion, difficulty speaking, or weakness or numbness on one side of the body; cold, pale, sweaty skin with a fast, weak pulse; heavy bleeding from anywhere, vomiting blood or black stools; a high fever with low blood pressure; swelling of the face, lips or throat or difficulty swallowing after contact with something that can cause allergy; or dizziness with abdominal pain or vaginal bleeding in pregnancy, or when pregnancy is possible (for example a late or missed period). If none of these signs is present, sit or lie down with the legs raised and drink fluids, then see a doctor if episodes keep coming back.